Look a little closer
A smooth bag and a visibly textured scarf can create different kinds of visual interest. Look first at the surface you can observe: fine lines, raised stitches, shine or an irregular grain. Avoid assigning a material solely because a surface resembles something familiar.
A note for your design book
Make a close-up and an overall sketch, then write one sentence about each. The close-up can describe texture while the wider view shows how much of the composition it occupies. Keep photographic lighting in your notes because it affects the appearance of shine and relief. The result is a visual study, not a measurement of roughness or material quality.