He could pretend to be a minion, and fall down after one hit, then get back up and do something destructive. Then, the party finds out that that was a fake BBEG, and he's actually over there, where the fireball is now inbound from...
There's actually a spell explicitly to do this, might be more powerful, but is also higher level (4, I think): Translocation Trick, from Spell Compendium