Well Compaq and IBM liked to do that on certain models still for a long while after, though they did it with a service partition, so it looks kinda like you're using onboard setup, but it's on the HDD... rather than using the floppy every time. Don't know if Peacock did that, not many other makers did. But if you use a linux boot CD or USB if capable and look at the HDD with that it should see any hidden partitions, which lets you know it's there but maybe got corruption or something, or misconfigured after someone messed with it. OR if you don't see one, that either says it didn't have one, or there's been a HDD swap or reconfiguration that nixed it. So really it's only a 50% shot it tells you anything.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.