Rob knowing about Jason

so i'm just creating this timeline

Ginny picked up morning day 1 same day jason gets enda and harold,day 2 jason strikes everyone in pt 3, day 3 jason get taken to hospital and breaks out, pt 4 jason goes back to crystal lake, pt 5 jason strikes

so rob says jason has escaped from hospital which he could have found out on 5th day as it was in evening paper, BUT he also could have seen the chaos at the hospital when they notice Axl and the nurse missing and jason's body missing

so to me it does make sense Rob did know about what was going on

I always assumed Rob filled Sandra in about Crystal Lake, hence why she wanted to see the original camp. So when she turns up dead, he put two and two together.