There are lots of ways to hide guns. One person who is a legal gun owner who doesn't approve of the law can hide them for his friends. Do not assume Illinois is united on this, enough voters are to pass a law, but gun owners consider this a tyranny of the majority and are sticking together
In a lot of rural areas where guns are most common the police don't approve of the law. They won't ask for a warrant in the first place. If someone else asks for one they will give plenty of warning to the person to be searched - or they will just take the warrant and throw it away without searching. If forced to search they will ignore you moving guns past the front door when they knock, then when the door opens find no guns in plane sight in the front room and leave.