Feng Shui?  He was walking down the street and realized immediately that the energy flow of your back yard was out of kilter, so he went in and made the adjustments.

&amp;#x200B;

Or.. he's a time traveler.  There is a rare toad living amoung your potted plants that will cure all cancer a hundred years in the future, and your back yard is it's last breeding ground.  Had he NOT moved your plants, one would have tipped over and killed one of the mating pair.

&amp;#x200B;

Or..He's really a pychic medium that was contacted by the spirt of the previous tenent of your house who was very OCD about gardening.  It was the only way to get the ghost to leave him alone- was to rearrange your pots to the ghosts liking.

&amp;#x200B;

Or.. He's been hired to drive you slowly insane.  He has started with gas-lighting, making you think that the pots move on their own or you have moved them and not remembered.  You  will be the recipient of a large fortune you cannot collect unless you are proven completely competent to take it on.  His employers want to make sure you can't collect when the time comes.