He had a phone in his hand as he walked by Jane. Partridge is an acolyte. We don't know how long it was between when Lisbon was first attacked and when Jane got to talk to RJ. That may not have been him drawing the smiley face on Lisbon (because that doesn't seem very RJ like, does it. It wouldn't be the first thing you see when you walk in... that being said she's not dead so it may be creep factor).
CBI Ron is always there. He can sneak around and see things without drawing suspicion.