Can I be arrested for possession of stolen property if I didn't know that I had it?

I live in Illinois and out of nowhere, all of a sudden I have police officers and detectives coming to my work and questioning me about things that my boyfriend allegedly did. (They think he robbed some stores in the area) They get a warrant for my house and car and they find some stolen blank payroll checks in my car. I had no clue they were there and no clue about anything that they were saying my boyfriend did, but since the car is under my name, they said that they could arrest me for possession of stolen property even though I didn't know they were there. But they didn't arrest me. I have no clue why, or even if they were telling the truth about being able to. I have absolutely no clue what's going on or even where my boyfriend is right now and they don't believe me. So I guess my question is, can they arrest me? And how do I protect myself from getting charged with anything since I really have no clue about what's going on?