This issue happens *frequently* with US Airways Dividend Miles, when you
make award bookings on partner airlines. Sometimes one segment is not confirmed or simply missing from the itinerary. Even though it appears on the itinerary confirmation email, sometimes it's not in the partner airline's system. I don't know if it is manual error or IT issue...

To be safe, you should always ask for:

- Ticket number
- PNR for each airline

Then with this information you check your reservation on the partner's website, or by calling them. You can usually select seats at the same time.

Also, a week prior departure, you should check again each flight in case there has been a time change and you have not been notified. Maybe you don't have valid connections anymore and it's always better to know it in advance rather than at the airport...

For the average Joe, of course there is no way for him to know those tricks, but it's easy to find alternatives at the airport when flying to LAS or FLL, and showing up at the airport 3-4h before departure.