thats so wierd! we have the SAME exact set-up ! We have a really big laundry/storage room with a dog-door in the side door leading to the backyard. When we aren't home we have occasionally let Gonzo have access to the laundry room with the dog-door open. I've never had this problem with him

When we were puppy-sitting my sisters Chi while she was getting married/finding a house (for 1 year!!), the Chi went potty a couple times in the laundry room when we had that set-up. She was a VERY prissy and lazy dog she also rarely left the house, except to bark at neighbors. To fix that, we crated her while she couldn't be supervised and gave her access to the whole house with the open dog-door when some one was home. She wouldn't got potty while we were home, she knew she'd be in BIG trouble . . she also got plenty of walks and exercise before and after going into her crate. Have you tried vigorously exercising Ruby before leaving her? That usually stimulates them to go #2! If you synchronize her meals and exercise right, you can get her to go #2 during walks or exercise while you're home, so she won't do it anymore in the house. Also try walking/jogging a mile with her before leaving and encouraging her to potty. That's all I can think of