I can be super deep in thought and it's like I'm somewhere else doing something else. (These imaginings are vivid enough to put on a TV that used VCRs.) 
Once I happened to check the time before I sat down on the edge of my bed. I was just sitting there and thinking about stuff while I was alone in a silent house. I "came back to reality" and checked the clock again. Three hours had passed. It's nothing that I can't control (except for intrusive thoughts popping up). So, I don't consider them to be hallucinations. I'd compare it to what you experience when reading a book. You don't just see text on a page; you see what Harry Potter's face looks like. 

So I'm wondering if getting lost in daydreaming is a common experience with us or if it's more unique to me. If this happens to you, why do you think that is? 

I also welcome suggestions on how best explain this to a psychiatrist without sounding like I'm saying "I see that are not there and hear voices that are only in my head"? 😳