But what if the middle man wanted to do a double closing to conceal a hefty assignment fee from the buyer?

A blast from a can of spray paint a half hour or less before open house time would conceal the sign ...

Box to conceal my address.I created a separate email account for the business.I only use and list my first name on my Business Cards.Sure, it's not fool proof, but it screens out the low hanging fruit that would want to get stupid if it were easy.

SF also passed a no-concealed weapons law..

There are paints/coatings available that will seal charred framing members and conceal the smell.

Is the seller’s agent action legal by concealing the bankruptcy information?

@Brie Schmidt hit the nail on the head - you are going to have to prove that the seller knew about the problem and concealed it. 

Concealed are 2008 high mortgage payoffs.

Then you will probably want to either conceal/encapsulate them (i.e. box them in) to ensure they are not disturbed or have all of the wrap on the exposed pipe abated.  

I agree with Phil Bottfeld that problems often conceal great opportunities.