There's no if-cell command, but there're two ways of doing what you want.
The easiest and most secure way is by setting a flag. This way, when the object is gone by using it, it won't be in the fridge again.
The other way is by using the if (has(objectname)) {-command. This checks wether the player has an object in his inventory. Off course, if he lost it later on it the game, it'll be back there.