Actually the Westin in Paris' bellman would come up straight up to you once you come out of the car/taxi infront of the main enterance, that's why what I said earlier would work if you went to that hotel (no check-in agent would even notice you). Just make sure they give you the ticket of course, it's their responsibilty to hold the baggage in a safe place. You can tell them while your going out that it's not check-in time yet and your gonna have a good walk in Paris then check-in later.