finders keepers
derived from an old children's adage "finders keepers, losers weepers",which basically asserts that anything found or discovered by someone automatically entitles them to ownership of that property.
"so that bag of money that fell off the armored car onto your front lawn...you gonna return it to the bank?"
"nope. finders keepers....so see you in Mexico!"
"nope. finders keepers....so see you in Mexico!"