If he lost his coins in an offline wallet, then chatting online is not connected on what happened, I guess he printed out his private key and someone stole it (maybe) or he accidentally put it on the garbage he throwed outside, then a certain person got curious about it and didn't waste the chance to steal those coins (lucky for that person) whoever got his coins.

That was odd because I am using also an offline wallet for years already but I didn't lost any of my coins, probably just a human error, in your friend's case.

E D I T: Please elaborate the situation, be more specific.