A non resident can legally carry a loaded CC firearm in his vehicle while traveling through IL as long as that person has a carry permit from their home state. Stopping for gas or taking a pee as long as the firearm remains in the vehicle your okay but it must stay in the vehicle. If/when you stop at a hotel just unload your gun, put it in a case and take it inside the hotel room with you, there are no laws stating you cannot do this. Also you are allowed to load the firearm while in the hotel unless that particular hotel has a posted sign saying they (firearms) are forbidden. The hotel room legally rented for the night is the same as you being in your house or residents. You are legally allowed to protect yourself while in that hotel room same as in your own house.
Also, in Illinois you are not legally bound to inform a LEO that you have a firearm on you during a traffic stop unless they ask, then if asked just be truthful and inform them you are passing through the state and you have a carry permit from your home state.
2shot