The absence of information doesn't give you any more details about the check than when the customer came to make the deposit. What you have there doesn't constitute reasonable cause. "Other bank won't verify" is never an acceptable reason.
Now if the customer says they won the UK National Lottery and needs to wire money tomorrow to pay the taxes on their winnings, you have reasonable cause. Of course, in that situation as well as yours, refusing to accept the check for deposit is the best option.
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