I don't think that is very satisfactory!
They are offering F lounges passes left right and centre, or offer platinum status just for cancelled chauffeur drive services, and they seem able to allocate status members flying business class to the front seats... but an actual first class passenger? Just left to fend for themselves? For a commercial decision aimed at improving their (the airline's) bottom line?
These compensation policies seem to be all over the place!
While i appreciate the only compensation the reservation agent may be able to offer you is a refund of points, that doesn't mean someone a little higher up can't offer you more. I would suggest this warrants an email to customer care.
Why should a platinum member, paying business class, get to thumb their noses at you and grab the First class seat you already paid for?