There are some items in the game that never respawn. It is ok because you will only need 1 of the item and need just 1 of the tool. Here are they:
Iron Ingot[]
The iron ignot is located under the jagged rock.
The Iron ingot is found by punching and digging a potato bush next to a jagged looking rock in the Teak area of the Cliffs region, as explained in the image. The iron ingot is used to make a Hammer.
FRP[]
Iron ignot
The FRP is located under a potato bush on Boar Island. It is used to make a Boat.
FRP