Okay um...

Going to have to say that working out it's definitely a Servant, especially Archer, is going a little bit too far in my opinion. That shouldn't be so easy to do even if you can tell you're being watched. In-Canon I can't recall any moment where it was that easy to work out.

Aaaalso the catacombs aren't meant to just sort of lead everywhere and let people bypass any conflict. ^^; They're meant to be a cool place to hide or set up a base.