Haven't received rent check but tenant says it was sent/cashed

[Lee Brewer]

I am a newbie landlord with only 2 units to date. My new tenant in my second unit is now delinquent for the month of July.  I contacted him and he says he mailed his rent check  and it has already been deducted from his account.  I told him I have not received the check and if it was sent and cashed then it was cashed fraudulently. He is in the process of notifying his bank about the situation.  What is the best way to handle this? Not sure if I should say it's not my problem and he is now delinquent so he owes the late fee as well as the rent that needs to be paid immediately? Should wait to see if he's able to be reimbursed from his bank for a fraudulent transaction? Should I waive the late fee if it does turn out to be a legitimate claim to a fraudulent transaction? Any advice from seasoned landlords is appreciated. 

Thanks