This also happened to me but I was aware people had viewed the room so I wasn’t surprised/I was expecting it, I just didn’t find it they were moving in until they were literally moving in lol. Disappointing you’ve not been kept in the loop but landlords are generally not the best of people in my experience so I’m not surprised they had one conversation with you one time about a roommate and then never said anything else until said roommate was moving in.
Hope the roommate is nice!!