Proving something like the curvature of the earth by getting some sort of signal over a flat surface is very difficult. The following set of video's will show that 1 measurement, however carefully done, is not enough. You have to look at all the different circumstances in which some phenomena could be proven right, or wrong.
Proving some thing is not easy, as a lot of circumstances might yield the same observation. That is why you have to do multiple, repeatable, tests, preferably on different locations, to see if it is a fluke or something real. And then you have to ask the question: How? And try to disprove your own observation.

So a group of people (Flat Reality Earth Explorers) set up a scene to prove a light source over the Monterey Bay

The video was shared across the community and commented on, e.g. by jeranism who elaborates on the video, and tries to explain the numbers behind the test.

So while this seems a good setup (they even explained how they did it),  the question that was not asked is: How? What explanation, besides the earth being flat, can there be that the light source was visible? Do my calculations match my expectations? Are there other objects, besides the light source, that can or cannot be seen? 

This video by GreaterSapien shows some of the things they forgot to check

In short: A lot of the lower part of the opposing side of the bay is not visible, but the light is? And the light source is even visible on the same height as the road, 10 meters above their level.

This video (by Bob the science guy) goes further and tries to compare two separate events, to see how that fits..

This next video (by Bob the science guy) goes even further and seeks an explanation of how the light could be visible at that height.


In short: The light is visible as a big blob and that has to be accounted for. Also the fact that it is visible on a higher point (the road) than it should have been leads to an example of refraction using a warm surface and cold air.

And even this might not explain the whole picture, because the question remains: Why is a light scattered and visible, while the shore is not..

Anyway.. this sequence shows that even though an experiment might yield a result, you can never proof something wrong, or right, from one experiment.