[mothered]

A refund method but slightly more interesting to me was to buy a phone, carefully open it while not breaking seals, put a display "dummy" device (for like $15 and are the same weight, size and appearance), switch the phones and return saying it was a gift.
What are your thoughts on this?

It called the sealed box method.

Given the objective Is to not show signs of tampering and the Item be placed back Into stock without checking the goods, you can put anything you like Inside the box. It will not be opened, hence what's enclosed Is Immaterial.