Ok, this ghost is quite sad and getting its treasure back from a goblin sounds like a very reasonable thing to agree to do. You head off down the tunnel and, not long after, do indeed run into a goblin that's busy going about chores. A long conversation (and two cups of tea) later, you find out there's more to this story than you originally thought. It turns out, you see, the treasure is an engagement ring the ghost gave the goblin, but the goblin has broken off the engagement and does not want to return the ring.