I sold a MacBook Pro recently and I thought I had signed out of the device but it showing up as a device in my Find My app. I’ve tried removing it multiple times now.
Go to AppleID.apple.com and see if the device shows up. If it does, try to initiate a remote wipe and then remove the device from the list. If it doesn’t show under your list of devices for your account, I don’t think you have anything to worry about.