Once Stan's sure none of the others followed him back into the bottomless pit, he begins his search.
He didn't mean to immediately fall back in, but now he understands how the pit works—keeping things but spitting out people—he knows would've come here eventually. Ford said he hid his other two journals away. Could they be here, floating in the blackness with Stan's old tax returns and Soos's contributions to the Shack's suggestion box?
He looks everywhere, but they're nowhere to be found. Another dead end. He should be used to those by now, but it still hurts.