At the point where Indy is about to enter the Well of the Souls, he throws the Staff of Ra (just an ordinary stick!) down the hole before he lowers himself down. You can hear the staff bounce and rattle several times, but in the next scene when Indy is in the pit, he picks up the staff where it it leaning almost vertically against the wall. This one I spotted the first time I saw the movie, and has bothered me ever since.