Expungment in Illinois?

I was arrested when i was 18 for stealing a shirt (dumbest decision i have ever made). I was never charged with anything nor did i plea guilty. my lawyer cut a deal for me to do community service, I did it and the case was thrown out. I am now 20 years old and applying for pharmacy school in about 9 months so i need to get this expunged asap because they do a background check. After this is expunged will this show up on the background check that they do? Also, if i were to get in and finish the program, would I be able to get my license or would they be able to view the expungment? I am really nervous about this because I have done so well in all my classes and don't wan't my life to be ruined over one dumb mistake.