Good observation! It's a snapshot, but they seem to know when something hasn't been used in a while.
Was your card actually closed, and they re-opened it? If so, you're a rare and talented individual! That's hard to do. Did they tell you that they would report it as open from whenever you originally opened it, keeping the history? If not, it's showing as new, so that would explain the score drop. Mine was a card that I was angry at and parked it for a while, so since it hadn't reported for 5 months, I had the brief drop.
At any rate, I think you will recover very quickly.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007