you probably cant get miles on CO, but should be able to get miles for that return trip on USAIR as long as your kept your BP's and everything.
http://www.usairways.com/awa/content...e/default.aspx

p.s. from experience, sometimes they will take baggage tags as additional proof if you are missing certain documents.

To credit missing flight activity for any travel on a partner airline, write the Dividend Miles Service Center at the address below and include your name, address, account number and a copy of the ticket receipt(s) and the original boarding pass(es), indicating seat assignments. These documents must be submitted via mail.

US Airways
Dividend Miles Service Center
PO Box 025458
Miami, FL 33102
USA