I just lost 2 mil JPCs because of a bug.
It wasn't "because of a bug".
It was because you don't have the private key for your coin address and never did have.
Always print it out before you do anything else after creating a new address that's going to contain a significant amount in it.
nah he just a backup of his wallet, don't need your priv key everytime, better to save the whole wallet, because there are hidden address