1ST SENTENCE

Sam said "Hi Dada!" while waving at Mark.
She has been saying "Dada" for months, and has been saying "Hi" for about a week.
But yesterday she used them together. 

So now Rick and Mark got into a discussion yesterday about what constitutes a sentence or complete sentence. Do you have to have a noun and a verb? Does Sam's sentence count? Does it count, but she just has bad grammar? Paka Rick is trying to NOT give her credit.