Amen to this. Our flight from PDX-SFO was cancelled. I called the 1K line and they put us on a later flight. When we arrived at PDX last night, the ticket agent told us that our travel agent (Travelocity) also rebooked us on an earlier flight and therefore cancelled our reservation.

Advice 1: Reconfirm your reservation with United on the date of departure.

Advice 2: Never book with Travelocity.