Context: I am helping my friend with some computer problems. He got a new computer after his old one was stolen but he no longer has access to his firefox password. I am trying to help him log into his firefox sync but neither of us can figure out what his password is. We can reset it, but then he will lose all of the passwords he has saved to his firefox account in the past. We do not have any recovery keys nor is he logged into his account on any device. I have access to Mozilla Maintenance Service logs from before he lost his computer, but that is it.

Can we just talk to someone from Mozilla to try to prove that this is his account that he's just trying to access? Or can we retroactively request the encrypted files?