Re: Shirt found.
The night/morning she went missing there was bad weather in Iowa. Severe tornadoes hit not very far from her home. Perhaps even power out.
I seriously doubt an animal carries a shirt away. Why? However tornado winds carry objects miles away. A red shirt could be something could be nothing. However it is very suspicious.
Would also note those storm swollen rivers move very very fast.
Just an angle I'm not sure has been discussed or is even relevant anymore... Maybe the dogs were in the basement because they get nervous in storms. My Labrador has to be locked up and given sedatives so she doesn't hurt herself. If MT knew the dogs were nervous and there were storms in the area, she could have locked them up that night.