We had a sheltie pup who did the same thing when we went out. She always ripped up the same chair cushion in the sunroom. Our uni vet behavioral clinic told us it was called separation anxiety...the stress of being separated from her owner. She was ripping up the same chair because it strongly had my scent on it...it was the chair I sat on. They gave us wonderful tips of how to deal with the problem. One was to let her have her special 'cave' or 'den' place to stay in & to leave something like a towel with her that strongly had my scent on it. I used to put a towel in my dirty clothes basket overnight. Also we had to totally ignore her (no eye contact, turn back if she jumped up) for 15 mins BEFORE leaving home & 15 mins. AFTER returning home. Only when she was quiet would we tell her 'Sit' & then she'd get her pat.
But all the tips are in a great article from the American Dog Trainers Network. Go to http://www.inch.com/~dogs/training.html Then scroll a long way down to the very bottom. There's a green button labelled 'Directory'. Click on that...and the Directory page will come up. Scroll all the way down to the heading PROBLEM SOLVING under which you'll find Separation Anxiety. Click on that & a brilliant article will come up.