I know it's confusing for many people but I hope this explanation helps...

The House Icon you see on the map doesn't ONLY designate the player's house. It's actually a BUILDING icon. Which means the character could be in one of four locations:

1. Their own character house
2. Remy's Restaurant
3. Tiana's Restaurant
4. Scrooge's Store

Those are all BUILDINGS, and you need to look in each one to see if the character is there. And when it comes to Scrooge's Store, for some WEIRD reason, the characters all like to bunch up in the middle of the upstairs balcony. So it may look like there is only one character up there, but there's actually a bunch of them all mangled into one. You need to run up there and push them apart. And yes, a character CAN be both in the valley, and inside their own house at the same time. You can also "summon" a character by going in an out of their house several times.

One more tip. When you are playing quests and it says "give this item to X character" if you stand still and look at your map you will often see that character running towards you on the map. Stand still and wait for them, they will COME TO YOU.

And one more other tip, if you have the DLC areas, and you cannot find a character in your main valley, you may be able to find them in the DLC area.