Mama_Hound,
Since you’re new here, the answers your getting here may be surprising or hard to understand.
I know that when we tell you that your own eyewitness account isn’t enough evidence, it sounds like Chico Marx asking “Who you gonna believe, me or your own eyes?” But the fact is that many of us here would not believe in ghosts, even if we had the experience you did. It may seem irrational, foolish, or even crazy that we would trust the expert evaluation of scientific evidence over our own senses, but many of us would.
Why? Well that’s a big question: people learn to make decisions about what sources of information to trust through a lifetime of experience and (hopefully) critical thinking, and not everyone makes the same decisions. But everyone has had the experience of seeing or hearing something we later realized wasn’t there, and many of us here have read extensively about the limitations of human memory and perception and the ways even sane, rational people can be fooled by subtle things.
So when I, for instance, encounter something that runs contrary to what I believe to be the common scientific understanding of how the world works, I won’t just assume that because I saw it, it must be true. I’ll ask myself what evidence supports the normal view of the world, and what would have to be untrue if my experience is true. I’ll ask myself how likely or unlikely it is that those assumtions are untrue. (For example, if I hear the winning lottery numbers and suddenly remember dreaming about those numbers the night before, I’ll consider it extremely unlikely that the laws of probability and causality have been replaced.)
I’ll next consider what other explanations might account for my experience, taking into account what I know about psychology and human perception. In the example just mentioned, I might concider that I am misremembering my dream, or that it is merely a coincidence. I will evaluate how likely or unlikely these possabilties are. (The odds of my dream being a coincidence are, obviously, one divided by the number of possible lottery combinations. In other words, enourmously unlikely. I may feel very, very confident that I am remembering my dream correctly. I may judge that it is very, very unlikely that I am mistaken.)
I will then ask what is the least unlikely possabilty or combination of possabilities. In my example, the non-supernatural possabilities are both extremely unlikely. Either one of them, however, is less unlikely, based on my understanding of how the world works, than the possability that I can predict the future through my dreams. That either one of the non-supernatural explanations is true is far less unlikely than the alternative.
So even if I experienced a very vivid dream in which I clearly remembered predicting the next day’s lottery numbers, I wouldn’t believe that I had psychic powers. Not because I think psychic powers are impossible and nothing could convince me otherwise, but because I’ve thought clearly and rationally about what sorts of things should convince me and what shouldn’t, based on the knowledge and beliefs I already hold.
Most of us here probably think more or less the same way, and most of us here (even the ones who’ve had experiences like yours) haven’t seen anything that makes the existance of ghosts seem like the least unlikely explanation.