I heard a story about an architect doing a reno addition for a family in Mosman. It got to the last hurdle when the family pulled out because they could not afford to do the renos, nor to live there any more. When the family went to put the property on the market they put the condition to the real estate agent that no for sale signs be put up. The agent replied that apart from their house and one other, all the other houses on the street are already on the market.
Get a grip. They have no obligation to advise you of their plans to sell.
I agree that they have no obligation to advise me of anything. However, as one human to another, I find deliberate misdirection when I bring up the topic somewhat difficult. It is one thing not to advise me but lies and deception get to me.