For the past 15+ years we have been using a pull-behind driveway road grader to maintain our gravel driveway. My wife was under the assumption that the grader was left behind by her ex-husband. Since the marital property settlement agreement stated that she was awarded everything she had in her possession, we assumed it was ours. We were surprised one day when one of her ex-husband's buddies showed up, came onto our property, without permission and took the grader. He later claimed he is the owner. We maintained it and used it for more than 15 years never knowing this other party even existed. Neither party has documentation to prove ownership. Was this property considered abandoned? Which party has legal claim to it?