Minecraft wiki entry for Things_not_to_do, associated text: If the player does not have a high enough level pickaxe for the block they are mining, no item is dropped when the block is destroyed. A good indication of if the player is mining with the correct pickaxe is by the amount of time it takes for the block to be destroyed. If the player has been mining a block other than obsidian and ender chests for a long time, then the block likely drops no resources when destroyed and the player just loses the item they tried to mine. The player can just memorize which pickaxe is at least needed for each block over time.