A dinghy you say? Easy fix for that. Put a dinghy hangar on your own ship, but don't build a dinghy in it. Sail close enough to their dinghy and use the hangar to retrieve their dinghy. AFAIK dinghies don't obey the same decay timer as other boats, BUT they're the only ship in the game where you can take someone elses in PvE
source: Me - I've done this a few times where people have kindly left them in my shipyards