Sentence 1: John is 8 years old and was brushing his teeth. 
 Sentence 3: John checked his mouth in the mirror 
 Sentence 4:  Indeed he was missing a tooth 
 Sentence 5:  John looked around and found his tooth on his pillow 
 Option 1: Suddenly John realized he was missing a tooth. 
 Option 2: He just brushes the gums where his teeth are missing.