That may be true. My unit didn't have a thermal camera setup. However, we're not always looking for live subjects that will give off a thermal signature, and thermal cameras don't help with spotting inanimate objects. I would say we found signs of the subject's passage (equipment, footsteps) 80% of the time before finding the actual subject.
I worked with an imaging and aerial mission company in Colorado, and indeed thermal was used in the vast majority of search and rescue missions. Not useful for recovery, but for time sensitive operations it was critical.
