unless you're running a .500 lift cam and it happened to fall into that port and assuming it was fully opened and fell in just right I wouldn't think it would fall past the valves. I'd take the manifold off and check all the intakes ports and if you're valves are clear turn the motor slowly by hand and if you feel resistance stop

We were putting a motor in another firebird once and we dropped a bolt down the distributor shaft. Didn't have a magnet to get it out. Spent the better part of 4 hours cussing with coat hanger.