Just a couple of ideas as to who Dinclusin and Dromalius could be (and yes, I googled both- I love the references! They fit very well into the story thus far):
-Could Eames have taken something from them in the past? If Ann brings thieves to justice, could she have clued Dinclusin in to Eames' deception? I don't know what he could have stolen, especially if he doesn't recognize either of them, but maybe they were inadvertently affected by something he did?
-Was their business/well-being somehow affected by Robert Fischer's inception (or anyone else's)?
-Maybe Ann actually catches Eames in the act of stealing something, which obviously doesn't really ever happen to him. This clues him in to the fact that he is really being watched by this pair. Maybe she casually mentions later that she saw him.

These are pretty vague suggestions (that I'm sure you've already considered!) but I just wanted to try to help out a bit. I don't comment on fanfic much, although I should, but I absolutely love your writing and your depictions of these two. Thank you so much for your dedication to this fandom! :)