For some crimes there is a statute of Limitations.
Which means ater so many years, most cases 7, a person cannot be prosecuted.
The men that robbed Brinks in Boston years ago stole millions of dollars.
They buried the money and waited the 7 years, but just before the time was up one of them freaked out and turned them in and showed the police where the money was hidden.
He turned them in becasue he freaked out and thought they were not going to give him his cut.
Had he not turned them in they could have spent the money anywhere they wanted and even wrote books about the crime.
The problem with your reasoning is that they haven't been charged with a crime.
Another problem is that they're suing the rightful owner of the property.
Your reasoning sounds like finders keepers, but even that doesn't work since the mint could now sing the same song.