Thank you for the information!
The rat has eaten that plastic thing just to the right of the red area and made a round hole. The hole is about 2 inches in diameter - perfect for a rat to walk through.
I have a "snake" camera for home inspection. I looked through the area under the plastic all the way to the passenger side and have not found any rat poop or nest. Good! I will be checking the cabin air filter this weekend.
On a side note. I admire how smart these animals are. In fact we have pet rats. My wife and children love them. Our pet rats never bite you, very friendly, happy to see you, like little dogs. They love to sit on a shoulder and make chirping sounds.
We trained them to jump, walk through a tube and other tricks. They recognize "eat", "jump", "stop", "home".
Really amazing animals.
This makes it hard for us to kill wild rats.