Get a small magnet at the hardware store. With the cylinder off stick it to the flywheels and rotate the engine s l o w l y and them return the magnet to the opening. If thewre is anything in there it will pick it up. The telescoping magnet tool will work also if the magnet will fit between the crankshaft webs.
If the engine was running like that for a while it has probably gone out the exhaust. Check the edges of the transfer and exhaust ports to see if here is any indication of the piece going out.