I don't think you're supposed to do that... ie, list an item for a specific buyer.

Well, actually you can- I've done it before in similar circumstances- but I did it with the buyer on the phone and online at the same time. As soon as the listing was up, they clicked and paid.

If someone else comes along and pays for it in the meanwhile.... well, that's the risk you take. I wouldn't try to explain to the new/actual buyer that "You weren't meant to buy that b/c it wasn't meant for you'. It's not really their fault.

Interested in what others will say here, but I'd admit here that I took a risk that backfired somewhat. Since the new buyer has paid, sell it to them and apologise to the buyer you set up the listing for.

It's not your fault that another buyer came along, but then again you took a punt doing this in the first place.

Good luck 🙂