Answer:
The missing criteria is ''A model must store that behavior in the form of a "symbolic conception" that can serve as a sort of standard for the behavior.'', or the retention aspect of imitation.
Explanation:
When the student watches the music teacher play, all they see is notes being played. Because they have no prior knowledge of piano, they do not know which notes they are, or the names of the notes, which is the way that pianists are able to retain melodies and play them.
So, the missing criteria is a way to store/retain the behavior.