There has got to be an audit trail - change seats, change ANYTHING and it should show up. Either the original agent didn't quite get the seats but failed to tell you, or that the "new" agent you were talking to was hiding the fact that it had been yanked away from you by someone.

In the former case, this happens a lot with my bookings, which is why I'm sharing this with you - is that you must end transactions (abacus speak, known as ER, in effect, "saving" the details) in Res systems or else all you've done prior to that goes out the window .Most agents like to end the transactions in two steps, 1st when the flights are confirmed and PNR is created. They tend to leave items like FF no, and seat requests for the 2nd end-transaction.

Sometimes, a direct connect message from the res system pertaining to that booking (example: a confirmation from waitlist, notification of too short a connection - this can be anything), will interrupt the save process. When this happens, you look at the message and then start from basically where you last "saved" it.
Your agent might have had that happen to him or her, and then forgot to re-request the seats when ending the transaction again. No audit trails for those as it was never saved in reality. This is probably most likely what happened - cause those direct connect messages are very common - the agent must be on the ball to remember. That's my theory anyway.

Unlikely. Just my viewpoint(and someone will correct me on this) - but i Don't believe the PPS seat bump works. Even if it DID work, it may not necessarily be the PPS member's doing. He or she could have just asked for something general like "good seats" and the coordinator, aiming to please, might have gone and done the bump unilaterally for the member without his or her knowledge.