It happened to me on occasion.

Sometimes when I'm watching porn and trying to time me orgasm to something on the screen, it can "go weird" where I get really close and then try to hold off to stretch it out too long without cumming, so when I do cum, there is no semen.

Sorry for the bad explanation here but it is difficult to explain and it only happened to me a few times.

Actually, orgasm and ejaculation are two different functions. Through kegel exercises and breathing exercises I can orgasm without releasing semen (there is always a little bit, but not like during ejaculation).
It is possible that you and your guy experienced this.

yeah I can say for experience that if he had gotten off within the previous hour then maybe his resivoir ran a little dry. I have even had semen come out after I had relaxed a little bit cause the muscle tensness had locked it inside. so after 1 or 1.5 mins then a dribble comes out.

yeah guys can. especially if they've been wanking a lot or having a lot of cumming because from my experience (which isnt much though) theres only a certain amount they produce. also things like their diet and the amount they drink and the temperature also affect this.

anytime friend

its possible....sort of. There will almost always be SOMETHING that comes out, at least a clear somewhat sticky liquid and the amounts can vary. The only real reason he would have came without anything actually coming out is if hed all ready had a few orgasms that day and was literally "out of juice" haha

Sometimes guys fake it to though so who knows, lets hope thats not the issue though.