I had a similar case the other day. I’m not exactly sure what happened cause I made the bid and went to bed. But I won the auction and the seller received my TG. I then msg him asking if he could mule the amulet and said someone had outbid me and I had lost. I check the transactions and I had in fact won the auction but there was another auction from the same seller with the same item that had ended 2/3 hours after my auction had ended. Im not sure if this was a double auction post on his end, if it was a mistake/glitch. He ended up giving the amulet to the person who paid more of course and refunding me.
The dude was cool about it but if this is a bug it should be looked into.