Mr. Spinelli-Noseda, a graduate of Yale College and Harvard Law School, was a young and well-regarded partner in Sullivan & Cromwell’s Latin American practice, as well as the firm’s hiring partner. At some point in the past few weeks—it’s not clear exactly when—his staff bio was removed from the firm’s external and internal Web sites. A cached version of his bio was available for a time through Google, but now it, too, has vanished.

The legal profession tends to be transparent with respect to the comings and goings of its members. And unlike their cousins in business, risk-averse lawyers, with their 5- and 10-year career plans, tend not to leave one position until they’ve set up the next. When they do move, their transitions are trumpeted in press releases.

So this unexplained disappearance—part of a spate of mystery departures and downsizings in recent weeks—is especially intriguing.

AT LEAST ONE thing is clear in Mr. Spinelli-Noseda’s case. Removal from a law firm’s external Web site—which is subject to the ethical rules governing lawyer advertising, and must be kept scrupulously accurate—is traditionally a sign that a lawyer no longer works for a firm. For example, immediately after Sullivan & Cromwell fired associate Aaron Charney, who sued the firm alleging antigay discrimination, it yanked his happy head shot from sullcrom.com.

But neither Mr. Spinelli-Noseda nor a firm spokesperson returned multiple telephone calls and e-mails. During my most recent attempt, a receptionist asked me to hold for “one moment,” then placed me on hold for very many moments. Finally she returned and informed me that Mr. Spinelli-Noseda was “no longer with the company.” She said she did not have forwarding information. (Paging Darby Shaw!)

Partner departures, more common at other firms, are rare at a place like Sullivan & Cromwell. After all, S&C is one of New York’s—and the world’s—most prestigious and profitable shops, with profits per partner of $3.1 million in 2007, according to The Lawyer, a British legal newspaper.

If Mr. Spinelli-Noseda is no longer with Sullivan & Cromwell, where might he be? The firm made no announcement, nor did any rival firm come forward to proclaim a poaching. One rumor was that Mr. Spinelli-Noseda—who is of Argentine origin, and who has been involved with policy organizations such as the Council on Foreign Relations and the Council of the Americas—left to take a position in the government of Argentina’s new president, Cristina Fernández de Kirchner. But no announcement or news coverage of such a move has surfaced.

OTHER MYSTERY DEPARTURES have involved less high-profile individuals, but are no less opaque. Over at Thacher Proffitt & Wood—which, as a major player in the securitization field, has been hit especially hard by the credit crisis—additional associates were either laid off or strongly encouraged to leave, sometime in the past few weeks. (In addition, incoming first-year associates outside of litigation have had their start dates moved back to October 20, from a more traditional start date in early fall.)

It’s not clear how many lawyers were affected by the rumored reductions, what groups they were in or under what terms they’ll be departing (e.g., how much severance they received, if they were laid off). In response to an inquiry, the firm issued this cryptic response, through a spokesperson: “As always, we continue to talk to associates in the areas most affected by the market conditions.”

Many of the firms that have laid off associates or otherwise reduced associate ranks significantly—e.g., Cadwalader, Wickersham & Taft; McKee Nelson; Thelen Reid Brown Raysman & Steiner—have provided more information and details about the cuts. But as the economy worsens, more firms may decide to shroud such moves in mystery, to avoid telegraphing weakness to the outside world. Such news can frighten current (and potential) clients, and it can also act like chum in the water, encouraging predatory raids on talent by rival firms.

In normal times, so-called “stealth layoffs”—economically driven firings disguised as normal turnover or as the result of bad performance reviews—can be dangerous for firms. If word of what they’re really doing gets out, the firm gets tagged as both flailing and dishonest, which can impair recruiting efforts when the economy improves. But in times like these, in which so many firms are experiencing slowness and discreetly trimming their ranks, stealth layoffs may be easier to get away with.

YET ANOTHER RECENT and mysterious disappearance—one might call it metropolitan downsizing—happened when Dewey & LeBoeuf announced the closing of its Hartford office. On its Web site, Dewey touts the office as “strategically located between New York City and New England,” as well as host to “one of our firm’s premier litigation teams” and the center of the firm’s environmental practice. The office was said to be quite profitable, and its shuttering left some folks scratching their heads. In a statement, the firm attributed the move to “its global strategy to expand the firm’s resources in major capital markets throughout the world.”

What exactly does that mean? Here’s one rumor making the rounds: Dewey closed Hartford at the behest of a consultant, who told the firm that small-market offices would hamper them from truly competing with the Skaddens of the world.

This may make the closing a little less mysterious. (Although the mystery of why law firms so slavishly follow the advice of consultants remains unsolved.)

So are all these disappearances on the DL just a side effect of the instability currently coursing through the financial and legal markets? When times are bad, it seems that lawyers—who generally loathe ambiguity—take the discretion they deploy for their clients and apply it to themselves. Unclear times call for unclear measures.