Stealth reduces detection range, it does not eliminate it. If an adversary has information on the path the target is likely to take it makes things much easier.

Stealth reduces detection range, it does not eliminate it. If an adversary has information on the path the target is likely to take it makes things much easier. This is how a F-117 got shot down over the Balkans. They kept using the same route and someone figured it out. At the ranges MANPADs operate, a couple km at most, thermal stealth is effectively impossible.