I agree--in other cases it's not always obvious either, for instance, locating the change fee applied to a non-refundable ticket.

In any event, it looks like I need to call CO. The ticket was not linked to my CO FFN, to my surprise, but my UA FFN. I say "surprise" because when I spoke to the CO agent to request the UG, she said she had to replace the UA FFN in the record locator with my CO FFN, so that they could debit my CO account for the 20k miles. But this didn't happen, and as a result I can't find any record of the flight anywhere on either CO or UA.

It does seem really stupid that you can't look up a reservation by the conf# even as recently as 24 hours after the flight. Really, really, dumb IMHO, but then they wouldn't be able to make you cough up the $20 for the receipt.