Hey man,
Congrats on the approach. As another poster in this thread said, just by doing an approach you're ahead of most of the people on this site. Here's some feedback to fine-tune your approach, for even more success:
1. It's fine to open with telling a girl that she is pretty, but you shouldn't compliment on looks when you close a girl. By that time you should have gotten to know her, so you can qualify her on something deeper.
2. If you want to #close, do it RIGHT THEN. This shows high value because you're not hesitating. If you leave and come back, it shows that you had to think about it and work the courage up. In this case it didn't matter because you were probably doing other intangible things right (body language, voice tone, etc), but it's good to keep in mind for the future.
3. Try to establish some kind of connection before you close her. This doesn't have to be very long -- can even be as short as a minute -- but it will dramatically increase the chances of her picking up her phone.
4. You definitely have a chance with this girl. Call her, and if she doesn't pick up, call her once a day for the next three days or so. If it turns out to be a flake, don't worry about it. Either way, you did a good job with the approach and you're improving your game.
-Dan