Was he just leading me on?

It seems likely that he realized it's not a good idea to get close as he is traveling off on Wednesday. From what you wrote it seems you two hit it off and if I were him the only reason why I'd be a bit more formal with you after sleeping together would be the realization that I wouldn't be able to continue seeing you due to traveling. If he showed up to dinner, I agree he's still interested in you. Let him know how you feel and see if you two can continue seeing each other for the few times you can.