One time when I was a teen ager I was in my room reading old Readers Digest magazines. I was sitting in the room lying on my back with my legs crossed in front of me up against the wall and the magazine propped on my thighs. Like an L shape.

I heard my mother calling. Mama was a meany so I was avoiding her. But she was calling me and my sister. Finally I huffed and started to get up and I heard her talking. So I figured my sister answered her. I then heard my sister (I thought) stomp up the stairs to the attic slamming the door behind her. I thought "Woah she is in so much trouble." About ten minutes later my father knocked on the door and stuck his head in saying "What are you doing? Why didn't you get the book?" I said "what are you talking about I've been here the whole time?"

I thought perhaps when I got up I might have yelled a reply which she heard and just assumed I was on the stairs but I wasn't. But they said they saw me on the stairs.

I got freaked out and started analyzing the situation and right outside the door there was a contractor garbage bag filled with stuff that I would have had to jump over to go out. Also I saw my legs the whole time up against the wall.

I never figured out what happened.

You never discussed the oddness with them?
You sleptwalked? They were playing a trick on you? Maybe your doppleganger came to visit?
You and your sister look alike from behind? Your parents were astral projecting?

Sorry, I'm all questions.

It could have all been a dream that in later years you believed was a true experience.
It happens.
I recalled once, to my father, about the time we fished a creek in Montana and I fell in. And I was angry because I'd broken a new fishing pole.
Dad swore the event never happened, and that he'd remember such a thing.
I remembered it as an actual occurrence.
In later years, I suspected that I'd had a very strong dream, forgot it shortly thereafter, then remembered it years later as an actual event.

Or, you have had an Doppelganger. The word is German, meaning "double-goer," and is defined as a ghostly double of a person or an apparition.
This duplciate is often seen doing a certain task or something, and often witnessed by others. On rare occasions, the person actually sees his Doppelganger but most of the time it's someone else who sees it and confuses it with the real person.
It's a very old belief.

Who knows what happened? The mind plays tricks.

Well it wasn't a dream that's for sure because we both would have had to have it. We discussed it and my mother swears she saw me on the stairs. I was wearing a red and white striped shirt and after my dad came in I had on a grey sweatshirt I threw on because I got goosebumps from the whole thing and my mother said "You had a different shirt on when you were there."

I thought a doppleganger was someone who looks like you....off to check it out.

My sister was out of the house when it happened so it wasn't her. We couldn't figure it out. My mother swore that I was lying.

Maybe he was playing a prank? I know it's a sort of anti-climactic response but other than a double of you it seems impossible. Weird that he said 'you' wore a different shirt though. Weird sense of humour if that is what happened.

Well it's that or a doppelganger, but if that were the case you wouldn´t have heard it as I don't think ghosts can manipulate real-world objects.

bump

It has been reported in hauntings that an apparition is sometimes mistaken for a member of the household. See for example Grave's End by Elaine Mercado.

Or maybe a thoughtform or tulpa.

Sounds kind of like what happened to me about a week ago. I believe its a doppleganger

ReviewDude may be onto something. It sounds like all was not completely functional in your household so maybe one or both of your parents was playing head games. Or the explanation of an apparition that they assumed was you is logical if not probable.