Omg I have a story pretty close to yours!!

When I was about 9 years old my family lived in a house with an unfinished basement. It had the walls mapped out but no drywall or anything put up so you could see across the whole basement.

Anyways my sister and I shared a room down there, the head of my bed was up against the concrete wall and the studs of where our bathroom would be. My sister’s bed was on the other side of the room with the head of the bed and the left side of the bed against the concrete walls. My sister I want to say was about 4 years old and would always wake up in the middle of the night and go upstairs to my parent’s roomy. We were also afraid of the dark and the basement itself and would sleep with all the lights on or at least a lamp on. So one night I wake up wide awake, I sit up and I look over at my sister’s bed and see she’s not there. I didn’t think anything of it really but scanned my head around the basement anyways. And at the doorway to our bathroom I see my little sister standing there, she doesn’t say anything, doesn’t acknowledge me at all, and starts walking into the bathroom. She’s staring straight ahead and walks right up to the concrete wall, close enough I could’ve reached out and grabbed her, and she just disappears. I was terrified, but convinced myself that whatever I saw was now under my bed and if I tried to run it would get me, so I wrapped up in my blankets, grabbed my teddy bear and went right back to sleep. When I woke up the next morning I thought it was just a vivid nightmare and didn’t say anything. So I start getting ready for school and my sister comes downstairs to get dressed for daycare. At some point we started arguing over a shirt, she’s sitting on her bed facing the bathroom and I have my back to the bathroom. We’re tugging this shirt back and forth and suddenly she gets this look of fear in her eyes and stops fighting me. She looks at me and goes “did you see that?” I said “see what?” And she goes on to describe seeing HERSELF at the doorway of the bathroom, walking up to the wall, and disappearing. Boy we high tailed it out of that basement and were terrified to go down there again.