I have not yet upgraded my flash so I don't know if that has anything to do with this but...
I was mining today in the new mining area when my bags filled up and rocks/gems overflowed. They did not overflow to MY feet, however, so I thought they were not mine and the other miner picked them up.
Then I saw a message that *I* got a gem but I saw it fall on the other side of the rock at the other players feet and he picked it up. I checked my inventory and it was full.. neither of the gems chat history said I had gotten was in it.
The OP got a lot of sparkly rock and two gems before I realized what was happening and left.
Bug? Problem with the old flash player? I don't know but beware if you go mining :)