BigBill: I didn't see the original post but I sort of doubt it is a rik-o-shet. More likely a keyhole - usually results from a barrel that is shot out at the end (had some M-16s do that) or from a bullet too heavy moving too slow or even one too light moving too fast.
You would expect the shooter to know that his bullet hit the ground and not the target but maybe not. At what range did the shooter experience the keyholing? Mikey.