Why, this reminds me of a situation that I'm in now, except on the guy's side..
There's no chance you're referring to me.. are you..? -_-"
Not that I ever wrote any such note to the girl in question.
However, speaking from the guy's perspective, I would say that you should just go up to him and speak face-to-face. Talk it out. You never know, he may have a genuine reason for liking you, perhaps he saw himself in you and really feels that the two of you have a lot in common.
In my case, I'm extremely "curious" about the girl. Based on what I know about her, she reminds me of myself in a way few others have and yet I know so little about her and it doesn't seem like many people have gotten to see what she's truly like.
Thus, even if a romance of any sort wasn't to work-out, I'd at least appreciate finding out what this girl, who always reminded me of myself from a distance and yet whom I knew so little about was like.
I say, talk to him, for both your sakes. There doesn't have to be a romance, but you may both learn something.
I full-heartedly reccomend it.
Do be somewhat careful, of course, but don't fear talking.