Ok from all the times i've played the game and watched gameplays on Youtube, i never noticed this music that plays in the area right before entering the Grand Hotel. There's a cutscene where Joel and Ellie see two Hunters go inside the hotel and then Joel needs to find a plank, you can also get to explore the coffee shop in that area as well and there is when this music (which i've never heard in the official soundtrack) starts playing. It doesn't start playing right away, you'll need to wait a few seconds though. It's very soft, serene ambient music and i would love to listen to it all. I'm sure any of you who is in love with this game's soundtrack will like this music and i hope this i mentioned is enough for you to know which area in the game this takes place in particular.
EDIT: I just went through it again and it seems like it's just a very short song, less than a minute long so that's why i'm guessing it didn't make it into the soundtrack, but still, i'd like to find an mp3 to this theme. Any help would be very appreciated.