A little off topic but you mentioned stuff found in walls of old houses.
My neighbor down the street.
Went to insulate his walls from the inside.
He found they were stuffed with layers of old paper.
When they were peeled apart there was an old paper flour sack maybe.
With the logo from the old mill we used to have down by our small river north of town that was driven by a
water wheel.
It was in perfectly good shape,.. unlike your mouse.
The mill is a part of the history of our town of which very little remains.