I believe the answer would be implicit wording
The answer is "stacks." That is the object of the phrase, and since a person is searching for something ON the shelf, they aren't searching for the shelf itself.
The denotative definition of a word is its literal meaning. This would be the meaning one would find in the dictionary.
By contrast, the connotative definition is the meaning associated with the word. It is the implied meaning of the word.
For example, the words in bold have the same denotation but different connotations:
-- a beautiful woman
-- a handsome woman
-- a pretty woman
While all these words mean the same thing, they do not have the same associations.
