You win but you may get stuck paying the borrow costs still for a while until either the stock is tradable or whatever happens with the resolution of the bankruptcy settles out (the residual shares potentially have _some_ value). In practice, before that, your broker or whomever you borrowed the shares from will probably just declare it a loss and close it out. They'll then get a little something from the bankruptcy, maybe.

That's assuming a traditional short, and not something like selling naked calls. In the latter case they just expire worthless.