You are a teen and he is a teen. There are a lot of things that just cannot be explained at that age.
I would guess that he was afraid to admit that he asked you out and did not want to have the guys tease him about having a girlfriend.
The best thing to do is to simply ask him.
Yes, but he may not want others to know it. It is that awkward point in a guys life where he wants to have a girl but the guys will toment him for it.
Maybe he thought it was none of your friend's business. Maybe the question embarrassed him. Maybe he said that because you haven't been out yet.
Doesn't sound like a huge deal to me. As long as he keeps the date. If that goes well, you can ask him about it later.
Drop him like something you found in the toilet.