I'm in the UK, and have been with my wife for about 20 years, so the context might be different, but when I was young and single, that was a big red flag.
I know it's not the way you meant it, but back then, the girls who did that were generally hard work. There was probably an 80 / 20 chance that they expected you to buy them drinks all night, and were just doing it for the free drinks. If you didn't buy them, they'd grab the next guy who looked daft enough to fall for it.
Unfortunately once you've been caught out by a few people like that, you tend to be suspicious of the genuine people too.
Probably the best thing you could have done afterwards was to buy him a drink and say something like, sorry, I didn't mean any offence, and leave him alone. Let him make the next move if there is one.