I did the same thing once on my computer at work. LOL. I had to call the computer repairman. I have no idea how he fixed it, but it only took him about thirty seconds and all he did was push a couple of keys on the keyboard. Then my boss got a bill for $75.00. Yikes.
Many display adapters come with a feature that allows you to 'turn' the display either 90 degrees at a time or 180 degrees at a time.
Mine is off so it doesn't do that, but not all adapters have that feature either. In my case it is NVIDIA NVRotate and there are no short cut keys you have to open the NVIDIA display menu to get to it.