The finder of lost property acquires a possessory right by taking physical control of the property, but does not necessarily have ownership of the property. The finder must take reasonable steps to locate the owner.[1] If the finder shows that reasonable steps to find the owner have been taken then the finder may establish that the required mens rea for theft, the intention to deprive the owner permanently, is absent
Legally I'd say it comes close to the description of 'theft by finding' 'theft by finding'
Well that would be admitting liability and end you in big trouble. Best would just be to ignore any messages.The naughty part of me says email the seller asking how much are they willing to offer to get it back
Very blurry situation. Not sure what I would do. I wouldn't judge anyone either way.
How exactly is it blurry?
Despite all the legal loopholes of whether its is or isn't theft, that isn't relevant in the slightest. Strip everything else away, and take it to the morality of the situation.
If it comes down to whether morally he should or should't keep it - shouldn't keep it will win out every time. So therefore - he should send it back.

What 3 weeks of wasted time?
He ordered something three weeks ago and got a refund on it 2 weeks ago after he raised a dispute.
It turning up now in no way constitutes '3 weeks of wasted time'
Keeping something (supposedly expensive too) that doesn't belong to you because you feel put out that someone took a while to send it and didn't respond to your emails in the manner you liked is only morally 'very blurry' if you're completely bereft of any moral fibre IMO.
I'm not very sympathetic to businesses that dodge out of bad contracts unlawfully.

How have we jumped to 'unlawfully dodging bad contracts' from that?![]()
I'm not very sympathetic to businesses that dodge out of bad contracts unlawfully.

By raising the price of the item afterwards.