Originally Posted by PVDtoDEL

Hmm. That's weird. Really weird.
You can ask the OZ agent to contact US and request that the ticket be reissued using the OZ flight number. That will definitely work, but no guarantees that OZ/US will do it. There is a good chance that there is no problem, but this is an unusual case that I've never seen before, and it's very possible that the ticket hasn't been pushed to OZ for some reason, which can create serious headaches at checkin.
If nothing can be done, just show up at the airport with the ticket number. Assuming that the flight isn't overbooked, the agents should be able to deal with it there.