I lost a lot of bitcoin when exchanged closed many years ago. Also I did loose some private keys, because keeping private keys was much more complicated a few years ago.
Most of the friends around me were cheated out of Bitcoin by scammers. When my friend transferred the address, he was familiar with a few letters, so he was not suspicious, and then the coins did not arrive on time before he realized it.
Can you explain more how this scam happened and how much your friend lost?
Bitcoin scam is common in today's space and I'm usually used to it and able to detect the scammed coins in the market. The entire market is all about information and getting the recommendable tools for projects available. Losing bitcoin to scammers presently is either a big mistake or ignorant of the right information, so I blamed the victims for not gathering solid information and also their greediness will lead them to been victims of malicious scammed projects in the space.