ACCOUNT LOST FOR NO REASON

I have a Microsoft Account I just can't remember. I had it linked in my PS4 for 2 years. After a recent update my Microsoft Account was unlinked for no reason. The Account Section in Settings doesn't even show a thing. Why is it happening? I don't have the ability to play in servers. I remember my username, P500GamingOnYT. Is there a way at least to find my personal info about this account or link another and don't lose my stuff. That is to say, I have purchasable items and I don't want to lose them if I connect another account.