OK, then it is a connection, not a stopover. It should be your choice whether to check luggage through or not. You get to choose whether to have your unlocked bag in an out-of-the-way corner in the bowels of O'Hare where any of 200 people can examine it unobserved or whether to retrieve it, keep it with you, and bring it back the next morning.

I agree with those who recommend getting a hotel room near ORD. You have 14 hours on the ground. Figure in your hotel room by 2130 Saturday, alarm set for 0630 Sunday.