And someone else suggested he just went to Tolkientown.com and picked up a fresh one..... ;^)
C'mon down to Tolkien town!
Well, at least in the movie, he already had it back by the time he faced the Balrog. He used it to bring down the bridge. I guess when he was in Rivendell the initial time, during the Council, was after Saruman but before Balrog, so I suppose that could be the case. I think I have the timeline right...