How to get copies of bank statements if you don't know account number?

Well if you had HSBC, you may have a problem, because they no longer operate in the US. Your best bet is to take your ID to the branch where your accounts were held and speak with a bank officer.

If these bank statements are from your own account that was closed, the bank will request your ID and probably will charge you per page.

If these bank statements are for someone else, then you would need financial Power of Attorney to obtain said statement, and again probably will be charged per page.

I can understand people not keeping old statements. My limit was the past two years, but since I am getting older, guess I should start keeping a 5 year look back limit.

Whose account was this? Are the bank statements for a Medicaid application?