Maybe it was the prior decline that was unjustified. What happened since August is that Abercrombie had a good Christmas season, which is absolutely essential for a stock like this. Abercrombie makes its serious money during the holiday season, the rest of the year the stores are open just for show.
BTW, I tend to agree with texmex that the rally for Abercrombie may be running out steam. I also wonder whether the takeover talk about Gap has benefitted Abercrombie, a much more popular company right now. I have always been skeptical about the prospects of Abercrombie as a takeover target, but that can never be ruled out, and of course the market is not required to share my views.