I can't say for sure because obviously the examples aren't provided, but this has happened to me several times before, where I saw almost my exact posing for a YCH used in others, and each time it was simply a coincidence. Unfortunately with how intense the fandom fixation is on YCH's right now, Generic poses or concepts often get accidentally reused or redone. Heavy referencing with YCH's are hard to verify, because of how often poses and themes are redone over and over.
Like I said, I can't see any samples, and am not necessarily saying *this* is just a coincidence. Simply that, if it's not, it will be hard to prove, and a lot of people would argue that it doesn't matter anyway, as it seems to be perceived as a grey area to use similar poses.
This artist *could* very well be copying off you- I do see the offer of money as pretty suspicious, and the fact that they are watching you doesn't really help the notion of innocence for them.