Virgin Media Is Loeb's Latest Score

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In its end-of-month investor note Feb. 28, the hedge fund Third Point LLC listed the U.K. cable provider Virgin Media Inc. as one of its biggest winners.

Virgin shares have skyrocketed since Feb. 5, when the larger U.S. competitor Liberty Global announced plans to buy Virgin Media in a $16 billion deal. So when and why did Dan Loeb, the chief of Third Point, get in?

A spokeswoman for the hedge fund declined to comment on the timing of the position. But Third Point's latest SEC filing, which covers the period ending Dec. 31, makes no mention of Virgin Media in its list of stock holdings. Nor does the hedge fund's January letter (although that's not dispositive, since the monthly letters only mention the firm's top five positions—either long or short — and its top five winners and losers, without mentioning other holdings).

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Given that Virgin Media was such a big winner, and that its shares have been range-bound since Feb. 5, it appears likely that Loeb got in to the U.K. cable company before the Liberty pact's announcement.

Virgin Media shares soared 18 percent on day one on heavy volume. (The volume doubled on day two, but shares actually fell a bit). Since that first-day pop, the stock has traded in and out of a very thin range, shifting in ways that would have led only to single-digit gains for an investor who bought Virgin Media after Feb. 5.

(Read More: Third Point Targets Murphy Oil)

Traders say there were rumors of a Virgin-Liberty tie-up in the days prior to the deal's announcement, but the shares remained essentially flat during that period. Since then, said one risk arb, "It's trading like a done deal." In other words, the stock runup may have already played out.

—By CNBC's Kate Kelly and John Melloy; Follow Kate on Twitter: @KateKellyCNBC; Follow John on Twitter: @CNBCMelloy