Ron,
Still no IR image to post?
What was behind you when you took those photos?
The left stain 'looks like' water entered under the vinyl, possibly from a door behind you, and then dried out. Sheet vinyl has a paper-like backing which is subject to wetting, yet that wetness (moisture) will not go through the vinyl to the floor surface (which is why spilled water does not do the reverse and go down through the vinyl to the paper-like backing).
Moisture under the vinyl, either leaking in from an edge of coming up from below, will, when enough accumulates, 'run to the low spots', which is what that looks like.