Small Engines (Lawn Mowers, etc.): Flywheel Key Location, screw hole, rectangular piece

Question
I took the right side of my 25cc/205 mph blower apart to free up the flywheel. The key - I believe that is what it is - fell out and I cannot find where to put it back. (Rectangular piece with what looks like screw hole in middle.) I've probably got the part names wrong, so excuse me on that. Can you tell me where the piece goes? Thanks very much.

Answer
If it  is in fact the flywheel key it should go between the flywheel and the crankshaft the flywheel slides down on to, to keep them aligned properly. Should be a machined groove down the crankshaft, and one on the flywheel it slips in between the two....Tom