Possibly

1) Could he have damaged the item by misusing it - doesn't want another because he realises that it can't stand up to the treatment he gives it.

2) Doesn't like the quality of the item so doesn't want a replacement

3) he already had a damaged one and replaced it with your original. (A lot of trouble to go to to get a "free" pan, more likely to be 1) or 2).   )