I grew up in the Bible Belt, so I got notes just like that at Halloween every year. It didn't stop at Halloween either. I waited tables in high school and college, and nearly every Sunday lunch, at least one minister would leave me their business card in place of an actual tip. Thanks for helping me put food on my table and gas in my car, ***.
Some protestant ministers also liked to ask if I had attended service that morning or if I had plans to attend services in the evening. As I was still religious at the time, I'd tell them that, yes, I attended Mass before going to work. Protestant ministers who knew of my Catholicism
never left me a tip (aside from the business card).
Talk to anyone who waited tables and pulled their share of Sunday lunch shifts and ask them about the Christian crowd. You'll hear stories. Lots and lots of unflattering stories.