repairs

Q: A person took his watch to a repair shop. Thereafter, the repair shop accidentally sold his watch to someone. What should now be done? Should the repair shop pay the owner the value of the watch or should they get the watch back from the customer and return it to the owner?

Q: About three years ago, I sent my phone for repairs. When I went to fetch it, they told me that they could not repair it, so I did not pay them. However, when I tried the phone, it worked. Do I now need to pay them?