which is ALMOST what the OP did. only thing left to do is what he shouldve done in the first place-- take the phone from his mom, and do what he knows is right and atleast attempt to find the owner. if your mom is to busy, do it yourself. give your mother a hand.
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and another thing-- if they do weed, then they probably could buy an iphone with their weed money if they wanted to, because they would need lots of money to buy weed, judging by how expensive i think weed is (i dont do it, im only 13, and this is a guess). but obviously weed is more important to them than finding their phone. but i still think the op is half-a$$ing his attempts to get it back to the pothead. drop your dang excuses and do some real recovery work to get it back to the guy, pothead or not
thats my 2 cents