When hair disappears, are these hairs dead?

How does one know if a follicle has gone dormant, and can produce a new hair or is dead?

There is no way to tell other than the timing of its disappearance. Recent hair loss often has some active stem cells trying to find the ‘missing link’ to grow out a hair follicle. After years, these stem cells are thought to be inactive or possibly dead, but nobody knows for sure because we can get them to wake up so we assume the worst.  If there is anything there, a small miniaturized hair left, medications might reverse it. Some people feel that microneedling might induce the recently hair that disappeared to come back. This is a microwounding process that causes the release of many kinases that can cause hair regeneration. When adding minoxidil to the process, results are even better. I referenced a review of mixroneedling here:  https://baldingblog.com/review-of-microneedling-extensive-thorough-from-reddit/