Detecting water damage?

This summer, I looked at a 10+ year old, 60ft-ish vessel that checked a lot of boxes. I was contemplating an offer, when it went under verbal contract. That buyer didn't move forward after flying in to take look. I had moved on to another deal which ultimately fell through. A couple of months later the broker called and said the owner was ready to let it go. Went back to take a deeper look and found what appeared to be water stains several inches high in the master closet which was cedar. I figured it could have been a lot of things and didn't think much of it. However, I found similar stains in another closet. The broker claimed it wasn't water damage, but it spooked me enough that I didn't move forward.

Now a couple of months later, I still think about that boat as a good fit and a deal at the right price compared to what I've looked at recently. I know if I survey the boat we could probably get an answer. Before I do that, I'm asking if there are any other ways to determine if a boat had water damage or what might have caused those stains. To my eye, the engine room looked clean and the engines and generators started up fine. The boat didn't smell any more musty than any other boat of that age and wasn't beat up. Carpet hasn't been replaced in several years (if ever). There have been 4+ owners and it was out of the country. Any advice appreciated.

It’s a convertible. I didn’t notice any rust or stains in the salon. The first incident I noticed could have been something like an AC unit from the engine room. The second wasn’t in an area with anything nearby that could cause it.

Hatteras, low hours for the year. Attached is an example of what we found in a few closets.

I appreciate the help and was intentionally avoiding detailed information so as to not trash a listing. I only have a few other pictures that show basically the same thing in different spots. A size limitation on the forum prevented me from uploading a higher quality image.

Carpet cleaning is a possibility and something I hadn't considered. One area looked to have an air vent close and another was near a sealed black panel. Obviously I could get a better answer at survey, but if I go to look again on my own I wanted to spot other tells. Occam's razor: it's likely fine but the owners didn't maintain it as well as other options in the same age range, despite what appears to he relatively light usage.