Also, remember, once stained, even if during construction, it will always be stained.
I put little faith in water stains on roof sheathing, gable end siding, wall sheathing were exposed to the interior, etc.. It just had to rain once during construction ... or any time since ... but my time machine broke a few years ago
so I cannot go back and find out just when the stain occurred and what the cause was.
Now, however, if it was wet when you were there ...