I took notes during the auction. The Utena sketch went for $2,800. I'm not sure if this is the same one you are talking about though, it was third to the last item. You should have stayed longer, the very last item for auction was a drawing board (don't know the character) by Takada Akemi, which went for a huge amount of $16,000!!!
I try to bid for a AX shirt though, but other people just seem to have too much money left over. ;_;