re: "...for the first time ever, my engine oil pressure light came on and stayed on.... For some reason, my engine seems to have dumped its oil!...."

I know this is going to sound crazy, but could you have drained the wrong fluid? I mean, drained out your engine's oil instead of your transmission's fluid?

There isn't any connection between the engine's oil system and the transmission's ATF system, so nothing you could do to the transmission could have affected your engine's oil pressure. The closest these two systems come to each other is via the heat exchanger inside the radiator, but it's still coolant, not engine oil.

Please don't take offense (it's not my intention) but the only explanation I can think of is that maybe, when you were under the car, you confused your engine sump with your transmission sump?

Using a ramp, it's a very long crawl to the transmission sump, whereas the engine is much closer to the front. Do you remember what tool you used to drain your transmission sump? The engine takes a 1" (SAE) size wrench or socket, the transmission doesn't (can't remember what, as I've never drained the sump as I wrote before).

I think that this may be the only possibility other than sheer coincidence!

I hope this isn't too serious (or too expensive). Hope the dealer sorts this out for you -- good luck.