Legal Question in Landlord & Tenant Law in Illinois

Depends what you want. If you just want your stuff, you unfortunately may be required to file a lawsuit called "replevin" which say they are holding onto things that you have a greater right to have in your possession. This will require proof of purchase. If you're looking to move back in because you didn't receive proper notice, your parents could counterclaim for rent. Police generally won't help in dispute situations like this but you certainly can ask. Before the sparks totally fly, I suggest you meet with a local attorney who may be able to help out.