I'd say it's almost certainly a business ticket. Fares that would be in First on a CO-operated domestic route will book into P.S. business class. I checked on Expedia and it shows business class for the $2800 round trip CO fare (same fare as UA publishes in Z).

I did not see any CO fares that would book into F on P.S.

Orbitz should give you a refund if you want to cancel. It would be good if you point out the mistake to them.