hahah cool modification of the story!!
because we have the same joke with a farm/ garden plot and the hidden gold beneath :P
basically a son called his mom from the prison and told her, that he's sorry that it's not possible to help them at the moment, but there is a treasure under their land :) and of course their conversation was investigated...
so the government went to their land and dug out all their empty gardens (but they couldn't find any gold) so the next day the mom called her son and reported what happened...
and the son said: COOL, i made up the story of course, but at least they plowed the ground instead of me, cause i was unable to do it now ;)
Ha, i think i've heard that one before as well
The other version is that the birthday boy calls CIA the next day saying that he saw his neighbor to hide the pounds worth of weed in the garden. So they plowed through the farm. Both guys laugh it out about the "return of favor".