The title basically says it all. Is there a way to detect if a sprite is destroyed so I can manipulate a different sprite later on?
What do you mean by destroyed? Is memory freed that was allocated to it? Answer to that is you cannot, but there is no need to do so; garbage collection takes care of freeing memory. When you release variable by setting it to null or allocate another sprite to the variable, old sprite is taken care by the system and eventually freed by garbage collection.