Yes - I think you have your answer now. The coolant had time to seep into the cylinder. Well, you're beyond my personal experience now, but I'd guess the reason you have a compromise in the head integrity is because it warped.

You'll certainly know more when you get the head off. There may even be a crack.

Someone here on the forum with more experience can probably tell you what tests need to be done to the head. I suspect that once you get it off the car, you'll need to take it somewhere for some kind of inspection and/or test.

Let us know how it turns out.

Ken300D