"Saw construction going on..."
"Honest, Your Honor! Sure, I was a little puzzled for a moment, but then I just assumed that I must be mistaken. It was late at night, and raining heavily, my glasses were broken, and I had a stye in my left eye."
Unless the Plaintiff acted in a ridiculous fashion, ostentatiously taking photographs, hitting the bars afterwards and bragging to everyone about the "big windfall" coming his way, it's impossible to prove - and he is under absolutely no obligation to "follow up" on any slight suspicion that might have momentarily crossed his mind.
Regards,
When you're asking a court for equitable relief, you have a duty to mitigate the damages. If you sit back and let the damages get worse.....ie let them go on building that house on your property.....that is what courts take a very dim view of. That's when they're likely to not give you some kind of windfall you were presumably seeking.