If the worst happens and it does fall into the engine, it's not the end of the world.
Chances are, it will fall down into the oil pan. , where it probably will do no harm.
Over the years, I have picked out many pieces of debris from oil pans, none of which caused any harm....... fuel pump arms, nuts/bolts/washers wrenches, sockets, pieces of intake manifold, pieces of timing chain sprockets etc. These things sink to the bottom of the pan and stay there. They are too big to get sucked up by the oil pump, so they just roll around a bit, thats all.