Your beef is with Travelocity, not United.

Are there United codeshare flights (with a United Number) available for the flights you want on United?

It doesn't matter if US Air is still flying those flights or not with their own number, it matters if United is offering it with a code share or not.

It's totally crazy to book a US Air flight as a United Code Share on Travelocity to save ten bucks for holiday travel. When something goes wrong, US Air will blame Travelocity who will blame United (or anybody but themselves), and round and round you go.

You need to get Travelocity to fix it for you.