He loaned some cash to a guy and he got paid back with the coins, and he isn't bitcoin savvy, so at this point I'm thinking it's either the guy who paid him back gave him a wrong instruction(whether onpurpose or not) or he accidently deleted the keys and don't remember.
In this case, it is very well imaginable that your friend got scammed.
If the instructions were to import an address, your friend never was in possession of the coins.
This is a relatively common scamming technique to scam people who are completely new to bitcoin. Usually done via blockchain.com, but works with any other wallet too.