Whole point being, WTF did you put it somewhere that there was even a question as to whom it was to go? In the OP you said that you ‘gave her the note’ when, in reality, that never happened.
A. Don’t give notes
B. If you cannot refrain from giving notes, then give the note to somebody that has business with it; don’t leave it around where some tool can take his pleasure with it.
Disclaimer: Of course, the world is full of strange people, and, you may very well be some Rico Suave, for whom the babes will overlook any kind of stupid behavior to get at you. If so, do what you want.
Years ago I included a note with my deposit slip at the bank. I think it just said "will you go out with me? " and had my phone number. We ended up dating.
In my experience asking people out with notes, it’s absolutely essential you write “Do you like me?” and include little check boxes with “Yes” and “No” options. That way there can be no ambiguity. The note approach has some risks for a grown man, but it has the advantage of letting the woman know right off the bat that you’re at least as mature as a 9 year old.