LOL the way you turned the JW terminology around, you made the return visit on your student!
For the rest, I don't think his age or that it was his workplace should put him off limits since he was set up to witness there anyway.
Also, not impressive that he didn't want to talk religion when the conversation wasn't going his way; I'm sure he'd have been fine with it if you were an "honest-hearted enquirer" (or sucker)
I'm sure you gave him something to think about, and hopefully made him wary of witnessing at work.
Personally I'd prefer to put the frog on lukewarm water and bring it to the boil slowly, but it takes a big investment in time, and still may come to nothing!