Gay, straight, what do labels matter? If a guy isn't interested in us because we are trans, that is their problem.... like you said, there are plenty of bi guys who would love us.
Personally, I assume that straight guys aren't interested in me. I have some male qualities that I understand isn't attractive to them (or even just the fact that I was born male freaks them out, that is fine). So, I wouldn't flirt with someone who was "straight" without telling them upfront that I am trans. Trying to connect with "straight guys" and keeping things secret in hopes that they will fall in love with us is just setting ourselves up for pain and being hurt over and over.
So, really, all you can do is shrug it off and forget about him. So you aren't his type, no biggy ~shrug~. It could be because the trans thing or because your hair color or whatever other endless list of "types" that people have...
In the end, the only thing we can really do is be ourselves and find someone who is interested in us.