I had a really terrifying experience last month and I have no idea how to feel about it.

I (22F) had planned a night stay at a hotel with my best friend to celebrate both of our birthdays. We’ve gotten to be very close this year and I trust him more than anyone else I know. I’ve never been uncomfortable around him or put off by him. That day, we had texted back and forth all day like normal. I was anxious about getting things done before he arrived (homework, decorating, wrapping gifts, etc.) but I didn’t have any anxiety towards him/spending time with him and was excited when he finally told me he was on his way. When he got to the hotel room, I did not recognize him at all. I let him in and figured that maybe I was just tired or stressed, but when we sat down I was incredibly uneasy. Logically, I knew he wasn't someone else. I had talked to him before he left his house and knew when he was at the hotel then walking up the room. His appearance and behavior were the same and a clone or replacement didn't make logical sense either. However, everything about him still felt wrong. The simplest way I can describe it is that the "vibe" that we normally had was off. I didn't have the usual feelings of being excited to see my closest friend and I didn't feel comfortable. I was really confused. I was trying to act normal because I also started feeling like I didn't know how he'd react if he noticed something wrong with me. I didn't trust him and didn't feel safe. But mentally, I was freaking out. If the person in the room with me wasn't the real person, then where was my friend? Was I in danger? How was I supposed to have a sleepover with someone who felt like a scary stranger? I tried to keep myself calm and convinced myself that it would go away, which it did after a little while.

That was the first time I've experienced something like that and it (thankfully) hasn't happened since. I think I pushed it out of my thoughts because I didn't remember it until a few days ago when I came across posts about other people's experiences with the same thing. Now, I can't stop thinking about it. I feel like what happened was not normal at all and I'm really worried that it'll happen again with him or someone else. I also worry that next time, it won't go away.

Is this concerning even though it only happened one time? Is it possible for me to develop an illness or delusion in my early 20s? The only illnesses/disorders that I know have been in my family are schizophrenia (cousin), mood disorders (immediate and other family), and potentially a personality disorder (parent). Should I mention all of this to my psychiatrist or is it likely that she'd want me to switch to inpatient? I'm truly so lost trying to determine if this is something to worry about. Typing it out makes it sound really bad but I don't know what to do.