I can understand this op. I have never felt that elusive 'spark' on a first date as for me, the 'spark' has to be about more than looks and I don't feel I know someone ell enough after one date to make that call. I guess i know if I absolutely am not attracted to someone but usually, if I've gone to the effort of meeting up with them, I know there is a good chance I will like them.
Last year, I chatted with a guy online for a few weeks and he was giving it all the 'when we meet up I'm going to kiss you', 'we're going to get on so well', etc and as soon as I got out of the car on the first (and only) date, I could tell he made his mind up that he didn't fancy me. My photos were also all recent, etc.
Turns out he was dull as dishwater in the flesh anyway so I wasn't too disappointed when I got the 'I don't think you're what I'm looking for' text when I got home! I was surprised I even got the text as it was so obvious there was no spark there.
I also dated a guy who, after our first date, I thought he was a nice guy but didn't feel a massive spark and assumed he felt the same but he texted me later to say he'd really like to see me again, so I did and we dated for 5 lovely months.
Maybe your guy just wasn't prepared to give it that second date to see if the spark developed, which is a shame but better than wasting your time I guess.
Sometimes, things just don't translate from paper (or online) to real life and there's no obvious reason for it.