I think the reason the coins were left in their buried state has more to do with the fate of the rebellion than the fact that they weren’t of use in the desert. I don’t buy that usefulness explanation at all.
Hard money is always of use at some future time and that’s exactly why it is buried. The owner doesn’t want it on hs person, but expects to use it later when whatever danger prompts him to bury it is over.
It is more likely that the Romans eventually winkled out the rebels hidden in the caves and either sold them into slavery or killed them. Thus no one was left to go back for the buried coins.