美国老土: need your thought please

I recently had an interview with a very big financial company. I met three people and the manager was especially happy with my experience. HR called me with the offer in a week and even went into details such as salary and benefit.

But when I asked her about their policy on employment sponsorship, she seemed surprised and asked me my current visa type. I told her I indicated in the application form - she put me on hold for a minute and checked my application. She tole me that she missed it and of course didn't tell the hiring manager.

I am currently on TN visa (a special type of working permit for Canadian and Mexicans) and I have been working for another financial company for two years. Obviously the HR person isn't familiar with this type of visa at all. So I spent several minutes explaining to her. In the end, she said she'd contact their legal department and the offer had to be on hold. As she called me in the afternoon, she said she'd call me back the next day.

However, she didn't call me the next day. So I called her at the end of the day and left her a message. Now another two days passed and there's no call from her at all. I called her office twice today and nobody answered the phone. Can you help me analyze what might happen? I am in a rush to decide whether to accept this offer (if it comes as an offer).

Thanks in advance for your advice.