Originally Posted by Wonderful Monds
It has to do with Brock being poisoned.
If you'll remember, when Brock was sick and before Jesse found out it was due to the Lily of the Valley, he thought he was poisoned by ricin, and accuses Walt of doing it. When he goes to Walt and has the gun to his head, he accuses him of having Saul lift the cigarette from him so he could poison Brock. Walt convinces him that Gus did it to turn Jesse against him. As we know, Walt's lying and Saul really did take it.
So that scene where he's going through his pockets, first he realizes that his weed is gone, and he knows that Saul took it because he tried to get him to ditch it right before he left. Then he realizes that Saul really did have the ricin pick pocketed from him, and that Walt really did set Jesse up and poisoned Brock.
Ok so let me get this straight. The ricin cigarette that is gone has to deal with the time Brock was poisoned. I can't remember if that was the first half of season 5 or season 4. Then when Jessie realizes that his weed is gone, stares at the cigarette pack he puts everything together?