Thank you all for taking the time and sharing your thoughtful replies. It helps to hear other folks' stories and that gives us some context. Much appreciated!
Tuesday morning, I tried all the things I had learned that might help us see signs of life - to no avail.
So, my son and I took him...
I have a Common Musk (Wild Turtle). I have had him since he was a baby. He is about 10 years old. Has lived in an aquarium where he has spent 99% of his time underwater. He got stuck/wedged under his fake log that has been in the tank for 5 years. He is at home is in that log.
Thursday morning...