Some people can be so rude.
I work in an office with 4 other people but today I am alone in the office due to sickness. A lady from the office next door to ours walked into our office and sat in one of the chairs having a conversation with someone with her phone on speaker, took a whole phone call of a few minutes with her phone on speaker and then walked out of the room. It wasn't even a business call.
She knows I am here and in the office because she has smiled at me several times while walking past our office and my desk is directly opposite the door so I am clearly visible to anyone walking into the room.
I have no idea what made her be so rude...