Does it really matter if you sprinkle it on top or sprinkle it on bottom before you poor your beer into the fermenting bucket. Obviously, I didn't sprinkle it on top and want to know if I messed everything up???
I can't imagine that makes a difference. Either way you'll only get half the cell count you could potentially get if you rehydrated. If you've got a super low gravity session ale then that's probably fine. Otherwise, it's worth the trouble to rehydrate.