The clock doesnt stop because he left school or didnt attend. However, depending on actual circumstances of his departure and return, he could file for the sixth year. I dont think it is likely though, if he did attend another school or classes at another school.
I ahve read where players got extended time due to going home to work or that sort of thing but I dont think it applies to Tillison.
FWIW, I have seen some posters list him as second team LB, based on participation they saw last Saturday. First 2-deep list probably wont be out until Aug 30 or week before EIU game.