Despite me having an account, that had both re-downloaded the game and played it just a few weeks earlier, had a custom character skin stored in it, and other stuff - they claimed I didn't actually ever own Minecraft, and demanded I provide proof of purchase.
I provided as much as I could - including security questions+answers (which I had stored in my KeePass database, together with the password) - but I could not provide the original purchase email, since I lost access to that email years earlier.
Their support was quite hostile with just the thinnest veneer of superficial politeness on top. They refused to tell me why they believed I don't own the game. They refused to tell me what I could do to get my copy back (other than providing that email, that I no longer had).
Basically I was considered guilty unless I could proof my innocence - and they wouldn't accept any other proof than the original confirmation email.
And that's how - after nearly 10 years - I stopped being a Minecraft player. There's no way I'm going to repurchase the game and play again - not after being treated like that.