I am an atheist and skeptic but I have seen something that might interest people.
I do have a possible explanation but I'm not sure if it fits exactly because it happened a long time ago. When I was five my cat died and about three weeks after she died I was walking down a small staircase and a blur the size of her came slowly down the stairs and back up in front of me. Now, it doesn't fit what I remember but it happened so long ago that my memory could have been distorted by time but occasionally I get blurry spots where goop from my eyes has gotten on my actually eye (sorry if that's completely disgusting) but like I said it doesn't match the memory.
Apparently this story alone is too short to post so I'll add my other unexplained story to make it longer.
I remember that I was little but not the exact time period, but when I was small I thought there was some thing named "the shadow man" trying to get me. I know this was my imagination but I remember clearly one time that a thing that was black and had glowing eyes came up from behind my bed (which was pushed against the wall so it wasn't the cat) and I hid under the covers and spent the night like that. After that nothing else happened and you could argue that it was sleep paralysis (so many things are) but I could move which I don't know if that fits the definition (I'll look it up and put it in the comments).
I thought maybe this would interest someone or help with a unexplainable event someone else had (if so please comment).