I'm not sure about Sabre/Virtuallythere.com, but if you have an Amadeus PNR for AA for example, once you log into
www.checkmytrip.com, you'll the AA Sabre PNR below the original PNR. For example for my future LH booking it shows
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">
Reservation code: ZXXXXX
Reference: Lufthansa - KXXXX
</font>