Pretend Open House ?

So I visited an open house over the weekend. The 2 ladies from Compass seemed least interested in talking to the perspective buyers. Something seemed off and lo-and-behold the house is under contract 1 week after coming on the market, and 3 days after the open house.

https://www.redfin.com/CA/Dublin/5582-Linden-St-94568/home/725901

This seemed like a 'pretend' open house which was just for show . Behind the scene, the seller or sellers agent may already have had a buyer finalized. Anyone else have similar experience or any stories to share?