Just catching up. I use fake eggs and it has worked well to get my ladies back to laying in the nest boxes whenever they get more creative. I did have one hen that laid 10’ up on the big collar ties that support the roof!
However, they do quite frequently inform me that while they understand my message with the fake eggs, and are open to taking my advice on where to lay, they are not fooled that they are anything but fake eggs. They inform me if this by tossing the fake ones out of the nestbox.
In the down feathers, it is possible Thelma is preparing to go broody. Mine often decorate their chosen nest site with downy feathers in the 1-3 days before going broody. I assume this is common behavior and hence the expression about ‘feathering your nest’.