Recently had a cleanout and sold an electronic device that I haven't ever really used. It was a case of do I just throw it out or put it on eBay. After starting to do the ad I realised I hadn't seen the remote any time recently so just listed it without it, it wasn't in the pictures but also I didn't state in the description that it was missing but sold very cheaply as the remote was missing.
I now received a message from the buyer saying the remote is missing and if I don't have it he will want a refund. The amount involved is pretty negligible so I will likely just refund if I can't find it, but more just annoyed at the waste of time.
Not that I can be bothered going down the eBay dispute path and wasting more time but curiosity has me wondering if I did what their likely response would be.
Sounds like the mystery device is very obviously something that comes with/requires a remote and you knew no-one would buy it without one… Give the buyer their refund already and stop wasting their time.