why the bleep is the AI allowed to delete your worker the same turn that they capture him? I am not allowed to delete workers the turn that I take them. I don't understand why it's so difficult to make the AI play by these same simple rules.

and no, this wasn't a worker form a different civ/city state that they were given the option to return. this was at the very beginning of the game...a worker that i built.

Yes. This is annoyingly unfair (and as it is nowhere mentioned, actually a bug).

Civ series in general bleeds the trope "My Rules Are Not Your Rules" when it comes to the AI. AI handles other AI and more than a few game mechanics so differently that you have to conclude that you're playing a different game from your opponents. This is standard fare in TBS.

High level civ V is sufficiently canned in terms of "abuse AI in trades FTW" that MP is probably a better venue for looking to play competition that is 1) using the same rules and 2) remotely competent. Actually, that's true of the entire civ series and most TBS.