Recently, I've been seeing/hallucinating people that I know and are still alive in places where they can't actually be at. I'll see someone like my sister waving at me and I can spend a few minutes looking at her, but when I actually start to think,"What in the world is she doing here?",she disappears completely. These aren't like memories or anything, the images are very real and only disappear when I start to to think about it. Is there some kind of medical condition behind this? I don't see anything abnormal like pink elephants doing the cha-cha. Is there anyother explanation? Could the people I'm seeing in my visions be trying to tell me something?