Massive steal at a Athena quest

My crew and I were doing a Athena quest but we got our ship sunk at the last fort so we re-spawned on a island near the fortress. There was a bunch of loot there for us to just take.We stole everything except for the chest of sorrows. After that we completed the voyage and sold. I thought we were just lucky at first but then I saw a achievement come up where it said I stole someones loot. I bet the other crew is seething back there at the island! HA!