One of my favorite Norman Rockwell paintings was found behind a false wall in the home of late Donald Trachte(cartoonist and illustrator). He bought the painting from Rockwell and very carefully painted a copy of it, hiding the original behind the false wall along with other paintings he collected. I'd seen the copy, which was loaned to the Norman Rockwell Museum by the Trachte family years ago. I think we were all fooled(which is a testament to Don Trachte's skill as a painter).
The only person I can recollect to have any suspicion about the one that hung at the Norman Rockwell Museum , was my friend James Gurney
he noticed some things were little "off" from the printed version.
Trachte's sons had the painting auctioned for 15.4 million dollars.