Notice also that the discard deck is at size 0. It might be a rare bug with discarding for prestige while hitting 0 draw deck size at the same time.
It might be a screen width problem. Use the number keys to select cards off screen (1=first, 2=2nd etc).
Judging by the width of what's visible on Rebel Base, that's not the case. The other cards in his hand that overlap have less width than what he does on RB, so it's his only explore card.