If the card is more than a few years old, it's possible it was a rewards card before they had "Quicksilver".
There are reports around here of a few people who had non-Quicksilver cards that were later auto-"upgraded" to Quicksilver, and a few who never got upgraded at all (i.e. they have cards that still only say 'Platinum' but they get rewards).
Also, I had an old HSBC 'Platinum' that earned 2% rewards that was auto-PC'ed to a Quicksilver One (and the rewards rate was adjusted to 1.5%). It did take a while (years) for me to get an upgrade offer to a plain no-AF 'Quicksilver', but eventually I did.
The thing about the QS1 is the annual fee; it's annoying to have an AF on a 1.5% card when there are no-AF 2% cards all around. Before my upgrade to the no-AF Quicksilver was available, I was able to call in and they would usually waive at least half of the fee, which made it a bit more tolerable. Pro-tip - they can only waive an AF after it's posted to the account.
Edit: minor typo
As I understand it from reading related threads, you can upgrade from platinum to QS but not from QS1 to QS, therefore the new QS1 might be a dead end instead of "halfway there", not to mention QS1 has an annual fee. I would call right now and tell them you never authorized the PC and see if you can PC it directly to QS instead. As for the mysterious rewards, do you see any new tools in the garage?
QuicksilverOnes can be upgraded to Quicksilvers, but the offers are less frequent than they'd be on no-fee cards.