
I went through that with my dad's 20 year old xbox live account like 2 years ago. They were insisting I couldn't get it back but after calling them over and over again we eventually were able to get it back. But we also provided our original purchase receipts from Minecraft, names of friends on the Skype account, and the serial number of every Xbox the account had logged into since the early 2000s. This was enough to convince them
At first we thought they were after his financial information because your Minecraft account is also your Microsoft account, which if you use the default settings also includes the entire contents of your computer hard drive synced up to OneDrive. It was enough info is one drive to drain all of my family's bank accounts and his bitcoin wallet and went around changing all his info. Only for us to be dumbfounded when it was just online playing Minecraft lmao.