What if you lose your iphone and get a replacement and then find it?

Literally just wondering I don't even have an iphone but these questions just bother me. If you lost your phone (for real) and got a replacement and then months later found it. What would you do?

Sell my first one.

Yes well what can you do, your new phone is now an old phone so who wants that not the shop, so you can do nothing but keep them both, I suppose.

If you're referring to an insurance company replacing it, they would block your old phone before sending you a replacement. If not, I'd just sell my old one.

It depending what phone plan you have but you won't get an iPhone

Then you would have two phones. But how would you get replacement for the lost phone?