Hmmmmm...
I think most people who are familiar with entheogens have experienced something that could be classed as telepathy. LSD is notorious for it, though I find Ayahuasca to be the most telepathic of them.
I think from your description that you got too focused on this, and had a bit of a "chasing your tail" trip. You would have been better off just going outside... taking a walk. Also, confronting person C seems like a waste of time. If he was trying to trip you out, there would be little point in getting him to admit it, and if he wasn't... he is either in a bad space (just thinking negative thoughts on his own), or you were projecting. Either way, there is nothing much to be gained from provoking him.
Whatever the case may be, there are certainly people you don't want to be around when you are tripping. It is useful to have a sitter, but it is also hard to relate to people who are not tripping. Kind of a Catch-22.
I suppose the big question is whether your friend (person C) is negative or weird in your opinion when you are sober. If he is the kind of bloke who would mess with you for fun, then you might want to reconsider being friends with him. If he is generally a good guy, and you enjoy his company, then you have to consider the idea that it was you who was having a negative paranoia flash.
Anyway, I wish you well.
HF