Thought I was low on coolant but now I'm not?

I was doing my usual weekend oil level check. I usually give a quick look at my coolants and brake fluid as well. It looked like both of my coolants were a little low. Mainly the left side, engine coolant reservoir. It was actually on the low marker, maybe a hair below. It's normally at the big plastic seam.

There I am laying bricks thinking that I'm going to need a new engine soon, right after replacing the HVB. I decide to go on a lead foot drive on the cold engine and then check the level again. Now it's where it normally is, as far as I can tell.

I can't come up with a reason this is. I've never seen it at the low marker before. I forgot to check the inverter coolant level after, but I'm not that worried about that one. I plan to keep a better eye on them. Does anyone know why this has happened? Is it normal?

Thanks,
Higgins909

 

Not sure how I double posted this. Maybe a admin can delete one of them?

 

I'm going to try and check it in the morning. The whole oil and coolant check and lead foot drive was about half a hour before I posted this.

 

I only looked at the engine coolant again and it was back at the low marker. I've only got about 1000 more miles until my next 5k oil change. Was wanting to do a 200k oil, coolants, transmission fluid, both air filters. Hopefully it doesn't get much lower in that amount of time.