In answer to the original question as to whether stress hormones would be in the blood even when not feeling stressed at a particular time, I think it would depend upon the nature of the situation.
If a person has been chronically stressed, I'd imagine those hormones would always be present. The same as if you are a woman, estrogen is always present, for a male, testosterone.
It isn't something that flushes out of your system instantaneously, and the effects of it would be seen long term in other areas of blood work, i.e. your cholesterol, lipids (cortisol increases your lipids), blood platlettes, etc.
Your body doesn't produce and use hormones in isolation. It's a very complicated web.
Why do some people handle stress well, and others not? In part (I think in large part) because of genetics.
I explained to the nutritionist that both my mother and maternal grandmother (as far back in my family that I have personally seen), as well as my brother exhibited symtoms of chronic anxiety. My grandmother and now that I think of it, brother also exhibited OCD.
Another brother died of alcoholism at 34, father alcoholic most of his life, "stiff upper lipping it" the last decade or so of his life. Other drug dependancy issues, including suicide attempts, with another sibling.
Given this history, plus my own personal life experiences, including outside stressors such as husbands health issues, is it any wonder stress hormones would almost constantly be present.
I'm not giving this information to interest anyone about me personally, but as a statement to everyone. My experiences are not unique, others have/had much worse backgrounds and experiences, others better.
The fact is, I have always found statements/advice such as "take a deep breath, hydrate, think 'happy thoughts', pray, eat more/less of this/that, etc." while well meant, to be many times inadequate. It may be fine for many people, but these one size fits all methods leave a lot to be desired. Telling someone falling off the cliff into the abyss of a panic attack to "take a deep breath" is like giving someone a kleenex and telling them to use it as a parachute when they are about to fall off a literal cliff.
You cannot tell stress hormones what to do, any more than you could tell FSH in a woman not to help produce follicles in the ovaries for egg production or insulin not to perform its job on glucose.
Going for a haircut, will be back to continue.