Perhaps your pleco was a little skittish from the move, and like Terry said, zoomed up to the top and accidentally flew out. I have noted in the past that new plecos will zoom around too fast until they get happy with the tank and settle down.
I hope he is OK. The pleco is one tough mutha.
On a side note, the other day I noticed one of my plecos in my clown loach tank swimming upside down all over the very surface of the water, it was a real trip to watch. He did it when I fed the clowns. Maybe he decided he wanted to try some of the clown food instead of algae, for a change.