If you look at your mini-map, you'll see people's faces on there ^^ It might be a little confusing at first, but you'll soon learn which icon corresponds to which character. If you don't see them on the map, they're in a building someplace, so you'll have to go inside each one to look for them in that event. Also keep in mind that as you build up FP/LP, characters will sometimes decide to visit your house. So if you can't find someone, try checking your room.
"Little scratches on people's hearts will be gone if they pat them from behind, but the humans don't know that." -Li'l Cactus White 2: 1636-5705-4662
Each building has a list of extra mini icons that tell you who is in it. It takes a while, but you will eventually be able to look at the extra mini icons and will be able to tell who are in which buildings too.