Finding certain items in the game is based on chance. If you found what you need immediately, you would finish the game in no time and wouldn't have a game to play, so it may take a few tries before you find what you need :)

There are however ways to improve the chances of finding object. You can get a Minion Potion to summon Minions, you can get the Gigantic Rock to have more rock to mine, or a Willow to get loads of Wood!