Well this still seems so strange. Melissa, if you are being hired as an alternate, then it’s just that. You have to have someone drop out for any of a hundred reasons before you get a primary. It happens all the time that alternates get hired.
If you are a primary, at this point I wouldn’t worry, until you hear something definative. In any case, get all the medical, pq and paperwork done as soon as possible, so you are ready to go. Often, the primary person lags too long on the medical and doesn’t get everything done in time. The only thing that can be done is drop them and bring in the alternate instead.
Keep us informed on what you hear.