Female Advice Please?

There was a girl who worked as a receptionist at my Dr's office. I really hit it off with her well... she made me forget about my ex who I struggled to get over for a long time.

I decided to call her at work and ask if I could call her sometime. She was genuinely flattered... excitement in her voice saying "OMG thank you so much". She then whispered her number to me to call her later. I called her the next day and got her voice mail saying she is out of town for a few days. I left a message.... gave it a week and she never called. I called back and left another message... it's been months and she never replied.

What would cause her to give me her number and never call me back? Aside from the obvious "maybe she died" excuse. If she had a bf that would have been the easiest excuse?

Thanks