Sophie was trained to always be aware of high ranking Diamonds, Outpost or not. I'm sure she attended challenges and such, possibly even congratulated him at times. If you decide he was working on Arcana stuff, it's possible they spoke then since Sophie was the Diamond envoy.

You might ask Vi about possibility of Lucas's little girl getting to know Sitara.

I would not be surprised to learn that Sophie instigated some sort of books on wheels thing for people at the Outpost.

I can't think of a reason why he would know anyone else, but am more than willing to make it work. He might know Tess if he has a critter.