I see several threads on the issue of confirmed awards becoming waitlisted (i.e. lost), but didn't catch any discussion if any of those had ticket numbers?

This just happened to me, but I do have a ticket number starting with 016. When I called, the United agent said the ticket number is just for United, and that EVA never confirmed the space (I think that's wrong). She said she's a very experienced agent and has seen this many times, but would do me a favor and open space on the UA flight SFO-TPE, but that she had no obligation to do so since it was never confirmed space despite the ticket number in the confirmation. Said this was a great deal for me since the UA flight is currently going for 170K miles and I "only" used 88K miles for the original EVA booking.

So for those with more experience than me, is she right that you can have a ticket number without space being confirmed? I always thought if you had a ticket number you are safe, but she insisted that was incorrect.