Look a little closer
A sketch shows intention; a sample lets you inspect how that intention appears in a physical object. For a small pouch, your questions might concern the opening, proportion and placement of a strap. A pleasing drawing alone cannot demonstrate comfort or durability.
A note for your design book
Write three questions beside the sketch before examining a sample. Photograph the relevant details and distinguish a change in appearance from a tested change in function. Retain both versions of the sketch with a date. This small workflow creates a design history without implying that an informal sample review is a full product test.