Shawn and Gus talk to Lassiter about the case as he is getting coffee and then Henry comes up with a truckfull of Shawn's things to donate to Goodwill in episode 1x13 "Game, Set… Muuurder?". Shawn fake proposes to Juliet in episode 2x08 "Rob-a-Bye Baby".
Source: Psych Adventure
Shaw finds Gus at a clinic on his sales route to discuss the case. Only appears in the extended international version of the pilot. in pilot episode.
Gus is talking to one of his clients on the phone when he sees something on the spelling bee broadcast on TV which gives him a clue on the case in episode 1x02 "Spellingg Bee".