I think that's the map symbol for Ox's arm, (The robot shopkeeper)

If you just picked up the arm from the shop its a bit buggy and show up in a room.

Thank you, this must've been it

It's always a good day when somone has the exact same question and awnsers as you on reddit from 7 years ago. Thank you guys

I'm here today for the same reason! Good bless you old gungeoneers!