Excellent - ta. Quite the audit trail needed to be followed, esp when the redeemed flight got changed a couple of times. The DSCs awarded a month after flying with no PNR ref!
Unfortunately it really is - which is why I keep a tally of credits/TP's for myself. So much easier.
Just recently I did a clean up as several TP related DSC's had posted, so I could update my records to reflect that - so I know what's "in play" and what's "to be used" (and done is done when all the expected credits are received and the TP is exhausted).
So the way I do it is:
a) original booking PNR and a date ref (eg: ABC123 - MEL-OOL 1/1/22. Cancelled to TP number: xx_xx_xx_xx password yyyyyy. I also include the value of the TP so I know how much I have to pay with and the TP expiry date (eg: 12/22)
then when I make a new booking with that TP I update with the new PNR and the value and dates of flight booked.
and finally I have a separate fun list if I expect DSC related to a TP (which is no longer a thing, but many of us still have a bunch with one of the offered options from last year). So I reference the boking PNR and travel date. Just as a double check.
Once the DSC post (which could be a few weeks-a month post travel) then I can remove all those references. Plus I also keep the email e-ticket confirmations (which again list the PNR in the subject line, which is easy to find) in a folder of such things. That also includes, of course, the original TP emails, and the associated "opt in" email confirmations that came with them (eg "DSC opt in for TP #nnnnnnnnnn). So again, I can clear those out since they're no longer needed as any kind of proof should things like DSC not post.
yeah it probably is a bit cough, but I can open the file (just a simple text file, nothing fancy) and see easily how many TP's I have with what value and when they expire and not have to login to a credit balance check or hope that maybe QF might show the info in my account page or whatever.
Not that this helps you of course, but it's a general view of the "paperwork" I keep both as proof and tracking.
it's nice to see the number of TP's / credits I have left dwindling