Google Illinois concealed carry prohibited places, and it will link you to the law. IF more than 50% of their sales is alcohol, they are required to post it. Duty on property owner.
(d) Signs stating that the carrying of firearms is prohibited shall be clearly and conspicuously posted at the entrance of a building, premises, or real property specified in this Section as a prohibited area, unless the building or premises is a private residence. Signs shall be of a uniform design as established by the Department and shall be 4 inches by 6 inches in size. The Department shall adopt rules for standardized signs to be used under this subsection.
What we have here is... failure- to communicate.