Hey first of all DOH#

Second I would say it unlikely they would get into the engine, it's more likely that the they are stuck in the box, so what can you do?
Personally I'd take off the exhaust and see if I could shake them out. It may take some time but better than the very remote chance they course some damage, it's just as likely if you start the engine up with the end can off they'll fire out BUT I'd still take the exhaust off.
Having done hundreds of engine rebuilds on two strokes, best if a little late bit of advice, "
always cover anything where anything could drop into".
For some reason bolts washers and nuts follow the laws of quantum mechanics EG they can be in two places at once in your hand and down the crank case or alive and or dead if it's a cat in a box! LOL!!
Good of luck!