There is a Sheraton located right in the Frankfurt Airport. Since you have status there, I would try that first. It would not hurt to act like you are checking out and just did not want to lug all that luggage to Paris for a few days. You also may want to check on lockers at the airport first. I use them all over Europe when I want to hop off a train and check out a town before getting back on the train. If you don't see any lockers in the airport, check the train station area of the airport. I just can't remember, since I usually hop on a train at the airport with luggage in tow.