It's not up to the bank to decide if there are proofs or not for an account to be frozen or suspended in this case.

Once a police department finds or is tipped of something unusual happening, a person involved in what they think is a suspicious activity they will investigate and take this matter over a prosecutor, if he decides there are enough proof he informs the bank and the bank has nothing else to do than obey.

As for disclosure of evidence in such a case, most countries have laws against it.
At this point the bank can't help the OP, his the only chance is to try and speed up his process, by requesting a meeting with his local branch of the police or try to contact the financial ombudsman in order to verify if his account is indeed frozen following a police request and is not a stupid mistake.