Hi - This is just my "guess" about what happened to you:
When you pay for and print your labels, you first get a message saying that it is obtaining the confirmation numbers, which are very distinct.
If you then print a SCAN form, behind-the-scenes, it associates these exact delivery confirmation numbers with the specific SCAN form.
Once you printed your original labels, you probably hit the button saying all your labels were good, which I'm guessing locks in the association between the delivery confirmation numbers on the labels, and the number on the scan form.
If you then void one of the labels/confirmation numbers and print and pay for a new label, but don't reprint a corrected SCAN form, the system wouldn't have any way of knowing that. When you present the SCAN form at the PO, they have no way of knowing that you'd swapped out one of the items. It also means the SCAN form didn't really log in the replaced item, although it most likely showed up in Track and Confirm once it went through processing in the city where you mailed it, or at a minimum, when it was delivered, since it was printed and paid for separately and was a legitimate number.
I just read in another post that if you forget to print the SCAN form, you can reprint it by going into history for that date. I never knew that before, but I'm guessing that this is what might have worked to correct the associations in your situation. I'm also thinking that might be the thing to do if you do multiple batches of labels in one day, say for a last-minute order, and then want to have a single SCAN form to take to the PO or present to your carrier, which they prefer. SCAN forms are only good for the date of mailing any way, so the only time it makes sense to reprint one is on the same day you're mailing the items.
This is just me trying to think through how the system must work. Hope it helps, and if anyone else knows anything different, I wouldn't mind learning!
