The fare calculation will either show "O" or "I". I can't think of a clearer indicator. Unless UA refunded miles to the OP, the ticket should still be issued in O..
At present the reservation shows I for that segment - to have it change to O, the ticket would have to be reissued.
I am pretty confident that a reissuing after departure of the first leg with a *A parterne award is not possible. Even electronic tickets would have to be reissued - so technically once the trip has started - they can't change to O.