Is this a good idea?

There's this girl in a couple of my classes I like. We've talks and laughed a big. I wan to ask for her number but every time I start to we get interrupted of she's in a hurry and leaves. I've gotten pretty good at making paper lilies and she told me that lilies are her favorite flower. Since we always get interrupted when I start to ask for her number, I was thinking about making an origami lily, writing "from: Michael" on one petal, "To Autumn" on another petal, my number on another petal and "give me a call or text" on the last petal and leaving it under the windshield wiper of her car (like a parking ticket lol). Is this a good idea? I don't want her to think I'm doing it because I'm too afraid to ask her in person, cause I'm not, I just can't get the chance. I wanna leave it there so she'll find it after class. What do you think?

Well I took a chance and left it. I got a text a while later saying "Thanks for the cute flower!" So I guess she liked it! :)