What did your friend do with his offline linux laptop?
It's a very safe method, to create a wallet using your offline linux distro.
From 2019 to 2025, there are already six years which are long time enough, and your friends made double mistakes.
Firstly, he used only one backup method with USB stick and even he made two backups with two USB sticks, it's not enough.
Secondly, he did not check these USB sticks too regularly to see whether they are responsive or broken so that he can make new wallet backups. By waiting for six years to check two USB sticks, he wasted a lot of time to fix any one of two USB backups if one of them is broken and is no longer usable.
Firstly, he used only one backup method with USB stick and even he made two backups with two USB sticks, it's not enough.
Secondly, he did not check these USB sticks too regularly to see whether they are responsive or broken so that he can make new wallet backups. By waiting for six years to check two USB sticks, he wasted a lot of time to fix any one of two USB backups if one of them is broken and is no longer usable.
Yes these are exactly the points that I pointed in the OP. It's sad that he did all these mistakes, and even more sad that he didn't tell me about his backup creation process. I'm certain that I'd help him save his money.
It is not that he was wrong, the only mistake was to have stored the file on USB stick only without considering other alternative incase of the USB stick break down.
He was wrong! There's nothing "not wrong" with losing your bitcoin when you follow an approach that's increased chances of losing the data you want to secure. He wouldn't have been wrong if he had dimished the probability of losing the bitcoin, but something completely unexpected with a tiny probability happened.
Like, let's say he had 3 paper backups in 3 different locations and suddenly α fire started in all the locations at the same time. That's almost impossible to happen, but there's still a probability.
The problem is that people still think that there is an absolutely secure method to store bitcoin. There's none. There all scale from perfect to pathetic backup methods, but none is 100% secure.