That 'unfelt' stress was part of a documentary I saw on TV some time ago. They had people living in a city and others living on the countryside have a simulated job interview and measured stress indicators.
While both groups said from their own impression that they did not feel much stress during the interview, those from the countryside had significantly lower stress levels. That difference was blamed on bacteria of the bowel's microbioma which enabled people from the countryside (because of contact to animals like cows in their childhood) to cope with stress better than others.
I think there is still a lot we have to learn about the symbiosis with our bowel's microbioma.