From wikipedia:The Streisand effect is a phenomenon whereby an attempt to hide, remove, or censor a piece of information has the unintended consequence of publicizing the information more widely, usually facilitated by the Internet.

I thought of installing a hidden camera, but the area is pretty small and stark, so really not too many good places to disguise or hide it.I have ordered a cage for a new detector, but if they are willing to disable a detector to break the rules, they probably wouldn't be thwarted much by a cage. 

You can't run away from it and hide. 

Wholesalers can (and a lot DO) get away with a lot more manipulation and hiding details. 

In this situation, do you believe they were trying to hide that fact and maybe pawn off any liens to the buyer?

(Those who have nothing to hide... hide nothing and the rest make excuses).

Could it be that some of the "no problem" home owners actually do have problems and are hiding that information for personal reasons? 

This is a back end transaction and hides the expense.I agree with @Russell Brazil that you hired them to do a job.

Often attics hide major problems under feet of blown-in insulation. 

You can do it above board instead of hiding in the shadows.PS - as a former Realtor, I don't have a dog in this hunt.