apple leather wallet detached and using the find my-shows a location a day ago?
Went and looked at that locations and no wallet found?
iPhone 7, iOS 11
The location of your wallet was the location of your iPhone when the wallet was detached from it. Once detached, the wallet accessory - being a purely passive accessory - cannot independently determine or communicate its actual location.
If the wallet wasn't at the indicated location, it had more than likely been picked-up by somebody else.