The hole could have exposed roots to dry air.

Yes it very well could be the chipmunks tunneling near your plants roots. I lost 2 2nd year clematis this way. We had to start live trapping and relocating these animals. What I thought last year to be 2 or 3 of them turned out to be 10 plus at the end of the summer. Good luck!

One thing that is *supposed* to work on the little beggers is wolf pee. An organic gardening store should sell it. Chipmunks can kill the roots by removing the dirt & storing their hoard around your plants.

I just let my cat out. :-)

I have issues with voles (a small gerbil-like critter that tunnels at or near the surface) and they ate all the roots of my first Venosa Violacea under the snow one winter. Other plants have had roots eaten and tunnels have allowed roots to dry out, so you have my sincere sympathy. Mice and other burrowing critters sometimes use the vole tunnels as well. Somewhere I read a suggestion that a snap trap next to a fresh hole and under a weighted down old plant pot (so you don't catch a critter that isn't doing damage) will remove many of the problem critters. I may be trying that route this year.