Kudos to you for not blowing the is it plugged in garbage at him and helping!
I can be as snarky as the next guy but when someone opens a thread like this it’s usually because they’re seeking help, not smart-assedness.
AFAIC the first rule of computers and computer support is never screw with the data! I remember receiving an SOS call from my (late) father, calling from out of state. He was trying to do good by backing up his computer and inadvertently moved instead of copied. Fortunately he hadn’t affected any system files but it did affect some applications.
This was in the days before remote access so I had to walk him through the restoration process - it can be daunting!