Where'd 4 go?

We gave Athena our old bedroom phone to play with. Today when I was making breakfast, I heard her ask a question so I turned to look. She was kneeling over her phone and asked "Where'd 4 go?" She said, "One, two, three... Where'd 4 go?" She looked at the phone a while, not knowing I was watching her and then pointed to it and said, "There it is!" I was quite impressed!!!