My guess is that it was a one handed opening knife. Actual switch blades are pretty uncommon. I have watched people who practice with these very common non spring operated knives.
They can open them in the blink of an eye. Just as fast as a true switchblade. I have several of them and because of arthritis, I can’t do the quick opening but can see how it can be done.
I carry something that fits the description. It’s a handy tool that only needs one hand to unpocket, open, use, close and pocket. Takes but a couple of seconds to open a fertilizer bag. It’s almost reflexive and doesn’t even need a glance.