Originally Posted by DJ_Iceman

It could have played out like this (just a theory).

You checked in with the TK virtual gold card and asked for a boarding pass where they saw you were earning UA miles. The agent could have thought that was odd or wasn't sure if it was okay, but she let you in and then went about researching it. Part of that would include calling up your UA MP profile which probably includes flight history, etc. Twenty minutes later another staff member came on duty and asked what her associate was doing. "Oh, there was this guy who came in earlier with a TK gold card but was earning miles on UA. In fact, he flies UA all the time so I wonder why he's not gold with us or hasn't bought a club membership! See, here..." They look at the computer. "That's weird," the new one says, "Print it out again and see if it switched to his TK number." They print it out, you come walking up and ask for your gate number...