I had this idea in college to buy a bunch of disposable cameras and self-address them. I would leave them in random places as I travel. The hope was for people to find them, take photos of themselves and their surroundings, and leave it behind somewhere else. Other people would continue the trend until the camera roll was empty and send them back to me.
I would get them printed and create a storyboard narrative of the photos based on these memories I never had.