Gone for 16 days, now peeing on rugs

- Our lovely 3yo indoor cat got out almost 3 weeks ago, and she stayed gone for 16 whole days until she suddenly showed up at the back door. Needless to say, we were thrilled! She had lost a little weight, but otherwise looked healthy. However, we took her to the vet 2 days later just to make sure.
- The vet said the only thing concerning on physical exam is that her gums are red and her teeth look older than her age. She did blood work (which we found out showed some mild signs of dehydration, but nothing to give IV fluids for -- vet said it would correct naturally), and she tried to get a urine sample but our kitty's bladder wasn't full enough to get a good stick. (Negative tests for feline aids and leukemia, too.)
- Now, in the last 2-3 days (4 days after getting a clean bill of health from the vet), kitty has started to pee and poop on rugs in the kitchen and in the bathroom. We thought it was behavioral, until tonight when - right in front of my husband and me - she walked to where we were, pooped on the rug my husband was standing on, and the poop was a sand/ivory-color.
- Our vet isn't open this weekend, and I don't think this is medically urgent enough to go to the 24-hour hospital or to go to a new vet for ... but what could this be? Is there some relationship between light colored/acholic stools and gum disease? Or related to her being away from home? I am thinking about going back to get a good urine sample to test. Any other thoughts? Or things to try to help this weekend?

Thanks!

Honestly - I'd call the e-vet and discuss it with her. If your kitty has a UTI, well, it's painful. She could have developed some health issues resulting from the stress of being lost, and those issues might not have shown up on the first check up.

My boy had struvite crystals - these issues never seem to arise during normal vet hours, but I beg you to at least call the e-vet. I really don't think you should wait til Monday morning. If it's only a UTI, wel, as I said, it's painful (I've had one, as have many women - you know you wouldn't wait 48 hours for treatment, if at all possible). If she's developing anything worse, such as a blockage - well, 48 hours could be deadly.

I know, I know - it's usually $100 just to walk in the door to the e-vet - and I've done it and driven home thanking God there are e-vets and I have a credit card.