I keep one of those "rare earth" magnet pickup tools in the box. The magnet is only about 3/8" in diameter and 3/8" long. So strong most SS fasteners will stick to it no problem. (yes most SS fasteners are mildly magnetic).
the screw just vanished. i wasnt watchig the kids while they were playing and they assumed it went into the hole. but we dumped the bike onto its side, cycled it through and looked in, but found nothing. it was one of the bigger screws. i was convinced it wasnt in there. they wanted to tear the motor down. we tried sucking it out, messing aorund with magnets, and wires, nothin. but we never found the screw either!
we're still working on getting it running. it runs on one side, but not the other, then the other side but not the first. freakin 40 year old coils and shite. anyway, my bike fired right up, buckys cb did, and his bmw. so, we'll see. bills still needs some work, ut itll be done for the school.
They got little bore scopes down to about $300 now. Gonna get one next time I'm ...errr...bored. RIGID makes one for about $200 with a little 2" LCD screen....but the camera end is too big to go down a spark plug hole.
PS. Maybe the screw fell though the hole in the piston?