I sent an email earlier to Asiana about getting a new confirmation number for my award itinerary booked through UA and they replied:
"Dear LTabi,
Thank you for contacting Asiana Airlines. We have received your inquiry and would be happy to assist you.
Unfortunately, for online seat assignment only passengers holding Asiana Airline ticket numbers will have access to do so. For prio seat selection, please call our US Reservation Center at 1-800-227-4262 and our agents will be happy to assist you.
Thank you for your patronage of Asiana Airlines.
Sincerely,
Customer Relations
Regional Headquarters, The Americas
Asiana Airlines"
sigh...