Benefit fraud...not guilty, but the bank doesn't like it!?

A little while ago myself and my partner were investigated for benefit fraud, The allegations were not true, and the compliance officer told us not to worry about it. Today we went to open a bank account for my partners son, he needs it for his EMA. the bank said we may not be able to open an account because of a previous fraud investigation. How did they know, and can that info really be held against us? If the benefits dept' found nothing wrong, then why was this info held?