My husband transplanted a sedum to an area under our bird feeders about ten feet away. The plant is 6 inches wide, 14 inches long, and the hole was approximately 10 inches deep. After removing it, he filled in the original hole. The following morning, the entire plant had been dug up and returned to the spot from whence it came! It was just resting there on top of the dirt, with no bite marks or other visible damage.
It's a suburban back yard in Massachusetts, in the northeast region of the United States, growing zone 6a. We have a number of regular visitors. I've eliminated chipmunks and rabbits for obvious reasons, so from what we've seen, the possible culprits include opossums, skunks and raccoons. According to what I've read, opossums don't dig. Skunks and raccoons do, especially when the soil is newly turned, because insects and other food sources are more easily accessible, so one of them may have uprooted the plant. We have no idea, however, what would have relocated it!
Unfortunately, my husband returned it to the same new hole under the feeders without taking any pictures, so I'm posting one of just the plant, and one including its surrounding habitat. The incident took place two weeks ago, and the plant has not been disturbed again.
Click on pictures for full size.