Hi, I have also had the same problem in the past. If I'm not mistaken after a certain period the device should disappear by itself. In the sense that the system should delete the devices that do not connect to its icloud user for a long time.
Alternatively, I had solved this by following the advice collected on a forum, you can change the iCloud password. This has the disadvantage of having to remember a new password. And also that you have to enter it in all your devices connected to the same account. But then only the devices that you have connected to the account with the new password should reappear. So the returned one should disappear.
Greetings