I drained the coolant out of the radiator last night. if I have to estimate, maybe 3-4L came out. Then today when I took the drain plug off the engine block....there was absolute nothing.....what does this mean?

 

Are all your coolant caps off? If they aren't they can cause a vacuum where it holds the coolant from draining. due to no ability to swap the coolant with air.
Be ready once you take the cap off it should just dump it.

 

^Yep. It's like putting your finger over a straw, the coolant needs a way for air to get behind it to flow out.

Dale