Randie said "I have to find her." I'd take that as evidence he's into her, or at the very least wants to see her again, regardless of his gender preferences.
I have no idea how any of the characters shown in this comic being transgender would impact anything. Doubly so considering if the girl who walked past Randie both exists and is trans, that would mean she has transitioned with regards to her appearance but her employer both has not updated their database to reflect her transition and (assuming that lack of update was for ideological reasons rather than "IT is too lazy" reasons, which I would assume a trans woman would apply pressure to) has not transphobically fired her. While not strictly speaking impossible, I find this far less likely than that Randie simply imagined the woman, or that one of his male-identifying coworkers had dressed in drag to mess with him.