I agree, if you're not sure, then text yourself and then there might be the polite short and sweet 'no spark' feedback or maybe not.
I would feel
about someone texting me to let me know Thanks, but no thanks, if I was already thinking the same and if the date's atmosphere has given that away already.
Should I have felt the spark and was head over heels or at least wanting a repeat, yes I would wait to hear from him and no answer would mean to me that he felt otherwise, and should I not be able to let it go, then I would contact and ask about a second date or comment on something etc. and expect no answer, or polite short 'no spark' answer or some rubbish, which then might open a whole can of worms should I fall for it.
I think men are generally quite simple. And I don't mean this in a bad way. I truly think if a man likes me then he'll find a way to keep getting in contact and try to get to know me...and I decide for myself what I want from him and go with the flow and see where it goes as long as I like it and am happy with it.
I also would be careful about interpreting too much into what a man says or promises, I am for actions speak louder than words and that over a looooongish period of time.