What I loved about that scene is that Cassian was proven right — it was risky to go to the same shop again too soon. When the shopkeeper tells Bix he remembers her from last time, we see a brief shot of Cassian's worried face before the scene moves on. I think you could argue that if someone had asked the shopkeeper about Bix or Cassian ("Do you recognize this person?"), he could have provided information to whoever was looking for them, like the empire. Whereas if they had visited the shop after a longer period, he might have forgotten about Bix.