You should call and ask your bank, you need photo ID to cash a check at the bank they'll have the check on file and the dates and times of the transactions, if it was deposited through an ATM into a private account they'll have that account information as well I believe and or the video surveillance from the ATM machine. Just call your bank and find out when and where it was deposited and claim identity theft.
P.s. How did they steal a check out of your checkbook without being close to you? And consider yourself lucky for $100 dollars, sounds like a kid.