I learned in my high school psychology class
that the sense of smell
is the sense that is most closely linked with memory
. As an experiment, we were given some vials of different smelling substances, and asked to write descriptions of how they smelled (before being told the information above). Sure enough, most of the descriptions written down were based on memories ("smells like grandma's kitchen", "smells like the dentist's", etc).
The point is, keeping an article of clothing that has belonged to a loved one and still carries their scent can be more effective and powerful than simply taking along a picture of them.