Depends on who invited you.
If your GF invited you then as the guy I would have just had separate tabs from the start.
However nowadays girls have become very bad at inviting their besties on "dates" and then expecting the guy to pay for them to have a girl's night out with him along as little more than the wallet. So he might have thought this was a test and felt pressured into trying to look like a baller and then regretted it later.
Could be that he is just a little thoughtless and it seems like ur bestie is too. What an awkward situation to invite you in on! That being said you didn't have to go and you probably should have stayed home. It doesn't sound like you are overly fond of this guy and combine that with being a third wheel and just an awkward situation all around.
However what you and alot of women fail to realize is that men feel social pressure and stigma, especially from women to cover the check. He probably felt that pressure, and under the influence of alcohol figured he would cover the tab, got the bill later and had a moment of sober clarity.
Either that or he hoped with enough alcohol he could convince yall to let him ride the tricycle and then when that didn't happen didn't want to foot the bill for ur night of partying.
The whole thing seems awkward from start to finish. Why would you have gone put with ur beastie and her BF without ur BF being present?
The dude sounds like a possible sleeze but it was ill advised for you to go in the first place. And to be frank, I don't see why you thought it was a good idea to go.