By any standard the boat is adrift and abandoned. Whomever "finds" it, either on their own, or at the request and assistance of the owner can claim salvage rights.
Assuming it is found by someone at the request of the owner, they will have already negotiated the price and details before they started looking, however if someone was enterprising and finds it and tows it to port, secures it, and watches over it, they have a legitimate (and legal) salvage claim right over that boat, and they do not have to return the boat to the owner until that is paid.
I'm not 100% certain of this part, but I believe the salvage claim can be up to 30% of the value of the boat plus expenses, however I believe it's normally limited to 10-15% if the boat is not in danger of sinking, or requiring of significant risk to the salvor to save the boat. The 20%+ claims are limited to extreme situations.
I salvaged a 27' center console adrift in the Drake Channel near Peter Island, B.V.I. (someone had towed it out of the marina pre-dawn attempting to steal it, but failed to get the engines started, so instead they set it adrift). The local police got word that I had rescued the boat shortly before it went against the rocks and had tracked down the owner by the time we got back to Road Town (We had first taken the boat to Nanny Cay).
We were given the option of going through the claim process in court, or accepting a $500 bar tab pre-paid for us by the owner at the Pirate's Bight Restaurant on Norman Island (out intended destination that evening). We took the $500 bar tab, ordered the best things on the menu and drank until we couldn't drink anymore, and told the bar and wait staff to keep the rest of the tab as a tip, which was around $125. We had told them early that whatever was left was their tip, so our drinks were extra strong all night

The next morning we returned our boat to the charter company and headed home.