That's where you make the unfounded leap that science is always right and the margin of error in human perception and recall is 100% ... In actual fact, as was pointed out above, science has its share of failings and is not always reliable. Still, certain things like the workings of human vision and recall are well established scientific facts. That's how people are able to get things like driver's licenses, by taking visual, memory and skill tests.
Now I realize the above opens up the floor to bad driver jokes, but seriously, think of all the judgements based on observation and recall that are made reliably on a daily basis ... literally thosands of them. In real life, our senses provide a vast amount of useful and reliable data. Add to that, that not only are humans amazing processors of sensory data, we are also intelligent.
If we had to prove everything we experience scientifically every time we need to make a decision, we'd never get anything done. So why don't we do that? Because we are intelligent enough to figure our way through life without doing that, and most of the time we do a pretty good job.
Humans have accomplished a lot, we're amazing creatures, just ask any skeptic who has had to debunk alien pyramid builder mythology. When it comes to that you'll get no argument. So why in an era of enlightenment, where we're more educated than ever before, when it comes to UFOs, do humans suddenly go from being amazing primitives, to modern frail incompetent, idiots who are incapable of telling the difference between a bug on a window and an unknown form of flying craft? The answer is obvious ... it's the skeptical bias. If you set that bias aside for a moment, and just be fair minded and logical, you'd see that there is value in anecdotal eveidence.
j.r.