How Keys Go Missing

Until we began our expeditions in house hunting, Spouse and I had no inkling of the various tangled tricks that real estate agents get up to.
Agents typically access an available property by means of a common key; the key is supposed to be left in its original place squirreled away in a quiet corner of the yard.
The trick is this: in order to ensure that an agent successfully procures the house for his or her own clients, they thwart all attempts of subsequent agents to view the house. The key frequently departs the area tucked snugly inside an agent's pocket. Interested persons arrive with hopes high, but cannot gain entry, and they cast wistful glances in the windows, shrug and surrender, and go home.
We waited last week to view a house. It was the middle of the day but we had been beaten to the post. As per the rules of house-buying etiquette, we shuffled about in the garden with our agent, kicking at stones and counting weeds and subtly weighing up the condition of the neighbourhood, while the earlier-birds explored the house with their agent.
The potential buyers seemed to take quite an age, but at last they stepped out of the house and pulled the door shut behind them. Our agent waited to collect the key.
"Key? What key? No, there was no key when I got here."
Our agent stood on the doorstep and asked once again for the key, refusing to believe that she and her clients had scrambled in through a side window.
Then raucous laughter broke the woman's poker face apart.
"Oh! This key! Here. Yes, yes. I totally forgot I had it!"
She threw open her palm like a cheeky flower, and displayed the shiny implement.
"That," she said, waggling her head gravely at the horrific state of the world, "is how keys go missing!"
"I bet it is," I fumed under my breath.
But that is not, and never will be, how houses are fairly and squarely acquired.