Hmm, interesting that it was a non-hierarchical group, since it seems so common for people claiming to be polyamorous seem to structure their relationships as very traditional monogamous hierarchies. Still, I always worry about "safe spaces", since that typically means that they have a strict political doctrine enforced through strict authoritarian anti-blasphemy structures.
I think that we often miss past lovers and friends, no matter the reasons which led to the dissolution. There is no real "shouldn't", I wouldn't think. Plus, it is nice that he made an appearance and wanted to be supportive, even if it were just a performative gesture.
I hope that your day went well.