The basement is unfinished, so the pipes are very easy to see there. I am quite certain he did not use any kind of moisture sensor anywhere during the inspection. I walked through the house with him as he looked around and would have noticed something like that.

The only mention of the pipes on the inspection report is "Condition: Satisfactory." He did find a waste pipe in the basement that was sloped improperly, but there's no mention of any testing/examination of the pipes.

The plumber who gave me an estimate said that using PEX can hurt resale value. I'm not worried about that now, but in the future, it might be a concern. Of course it's possible he was blowing smoke to try to do a more expensive job.