To add on to what bennator said, it's the right pillar, assuming your party is facing up at the start.

Your Move-Finder has to have a jump of at least 4. They should preferably be in a class with an innate jump of 4, so they can save the accessory slot for a Setiesmon or Vanish Mantle. If you don't want to get those, you should also give them Sunken State, because it's good to keep your Move-Finder invisible until they find everything.

To check if the Javelin and Escutcheon are the right ones, you can give someone Equip Change. Press Select by the new items to see their description. The weak Javelin is yellowish, and the strong Javelin will be brownish and say something like "Ultimate spear with matchless attack power.". The Escutcheon is on the left pillar, and easy to distinguish. It looks exactly like the Gold Shield. The weak Escutcheon is brownish and has a silver line across it.