Really? Did you have this conversation before you slept with him, and did he make any real promises that he broke? That wasn't clear from your post.
Or did you maybe think this and hope for it in your head, but not want to risk him saying no so you didn't really get clear expectations and relationship status confirmed by him before you slept with him?
It should be ok for you to admit to yourself that you actually really wanted to sleep with him and were afraid of pushing him for commitment before you landed him in bed.
In actions though, he acted like he wanted a relationship. Like by being on a dating site and his profile saying he wanted to meet new friends and maybe more. Like telling me he thought he'd found the perfect girl. Like texting goodmorning every day and goodnight every night and many times throughout the day. Calling to see how my day went. Asking every question about me and my thoughts on stuff. Sharing intimate information and asking about mine. Bringing me flowers.
I can't explain this very easily, but if you were with me on that date, and saw how sweet it was and all the handholding and snuggling up you'd have thought the guy wanted something more than a one night stand.
I'm not stupid, I don't invent things in my head, I carefully monitor people's actions /words and all that and I think he behaved in a way that made me feel it was going somewhere and the feeling was mutual.
He had also already asked me on the next date before we had sex. He'd said "next time let's go..." and I said "you're already planning next time?" and he said "of course".
I have had a fair bit of sex and a fair few dates and this was probably the most surprised I have been to find someone wasn't interested in me. I thought the opposite. Not to say I haven't been played before - I have - but the guy didn't snuggle up to me for 14 hours, laughing and stroking my hair and telling me about his childhood.
I wanted to sleep with him if I was going to see him again, I didn't want to sleep with him if it was the last time I'd ever see him.
Que sera, I was wrong. I don't harbour the guy any ill will.
I honestly wasn't afraid of pushing him for commitment, from the way he was acting I felt that was being freely given to me. I didn't get any sense whatsoever from the guy that he was interested in anything but definitely dating me more. It felt like a given to me, and if I misread that then he has odd ways of communicating how he feels.