Isn't it only the second episode since he left though?
This wasn't a bad episode I suppose, but some of it was still silly to me. Like Kara giving Mon-El a job that literally included answering a telephone & he didn't know how to do that. It seems like something she could've easily taught him ahead of time to make sure he knew what he was doing. Of course it didn't matter by the end of the episode as Mon-El moved onto something else.
Also in the ''real world'' wearing a pair of eyeglasses is not much of a disguise if that's the most important thing someone is using to hide their identity. I wanted Lena to say to Supergirl ''You look like Kara.''.