Stuff that can be face blindness (prosopagnosia) besides just "not recognizing someone" because I was thinking about it today
-Recognizing that you know someone without a doubt, but having no clue what their name is or where you know them from
-Feeling like you're supposed to know who someone is, but not recalling from where you know them (This for me usually feels like the "word on the tip of your tongue" feeling)
-Thinking you know someone and treating them like an acquaintance when you've actually never met
-Recognizing someone only in certain situations (for example, recognizing a coworker when they are wearing your work's uniform, but not out on the street) or when they have certain identifying features (a hairstyle, accessory etc)
-Recognizing someone in retrospect, either it randomly clicking into place or seeing them in a different context makes you realize who they were then
-Recognizing someone by sight but not being able to picture/describe their face without seeing it
-Being able to picture someone's face that you see often, but that image very rapidly fading when you're not around them for a few days-weeks (also goes for memories)
-Being able to picture someone's face briefly but it distorts or disappears entirely the longer you try to focus on it (also goes for memories)
-Recognizing someone now but not being able to rectify pictures of them younger or with a different look (such as before a haircut)
-Not being able to tell similar-looking people apart who are not identical twins (can be siblings or even unrelated) and therefore calling people wrong names or avoiding saying names in case you get it wrong
-Not being able to remember details about people because facts float in your head without a person or name attached and people/names float around without facts attached
-Feeling a lot of guilt, shame, and like you are a bad friend/bad person for not recognizing people, comparing/equating people to each other by accident, forgetting details and even names, etc - especially when undiagnosed
-Not recognizing your own reflection/pictures of yourself (especially younger/changed appearance), not being able to recall or describe your own face, etc. (dissociation can make this 100x worse too)
-Feeling very attached to a specific accessory, style, etc because you literally can't recognize yourself without it
Feel free to add to this if you experience something I didn't list