Getting a strong magnet down in a hole like that will be tough since it will want to clamp onto the sides as you try to push it down. I have a little three pronged device that might do the job though if you can get the thing onto the end.

Those two options failing I think I would want to drain the oil and if necessary use a funnel to pour oil or diesel fuel down the hole and try to wash the bolt end over to the drain plug.

I would be uncomfortable with it being in my pan. An engine has very fast moving parts in it and if it should somehow bounce up and get hit by a rod end it will become a bullet.

It seems unlikely but I would not risk it in my motor.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.