So, I would like to briefly describe my situation and I know that sounds totally strange and I could not find anyone on the net who has experienced something similar:

Three years ago, while taking a walk, I found a supposed object, a small transparent pyramid with a crystal in the middle. At that time I thought to myself: It looks great, I'll take it with me and put it on the shelf in my apartment. For three years I didn't think about it anymore and because nobody had mentioned it before, I didn't notice anything at first.

Now to the problem:

For three years I had something that wasn't really there. How did I find out?

Well, I once had a visit from a colleague, and I came talking to this pyramid again because of a conversation about collectible items. I wanted to show him the little pyramid that was on the shelf and I picked it up, but he looked at me totally confused and said: "What pyramid?" and I thought he wanted to make fun of me. So, I was like, "Huh, I'm holding it in my hand. Come on, stop the jokes" and he looks at me seriously and says with a straight face that nothing is there. I pressed the thing into his hand and when he took his hands away it fell down, but he said that he didn't feel, see or hear anything, as if he never had the pyramid in his hands at all.