At the entrance to Hushet Ruins, there's a spot that requires Toril's Skill Level - and, her level is not currently high enough to access that spot (so you'll have to remember it's there, and come back to it later.)
So, get the treasure on the first screen and then take the exit to screen two.
On screen two, there's a treasure behind a row of arrow tiles. You can't get that until you have the Heavy Ring (available at the Coin Exchange in Rizolt City), so skip it as well. (There's another treasure behind arrow tiles on the west side of the dungeon.)
Collect all the other treasure, and then head for the room in the northwest corner to get the Tophlus Flower, and then head back to Mosso Village.