Spotting the Fireflies.
Open your game.
Within five minutes you will see the mole, the butterflies, the otter and the fireflies.
If you don't ...he is there.
This means you have a place you can't see. Behind a tree, a building, etc.
This is the terrible part you are going to have to start at one corner of your farm and cover every square forcing these popup creatures to appear where you will see them. Leaving a place with open squares.
On my farm the only squares not covered is around the name Sucky. My Cat's name.
So move the machines, trees etc and start placing stuff on every one by one square. Sometimes close behind a building you have missed. Even under the ladder of Pipers Tree House. Then once I have tapped them I force close my game and start over.
In following picture I circled the fireflies, you will also see the butterflies.
If you have a hidden open square he is likely popping up in it.