According to Gouby:-
It makes logical sense that there would have been very few high grade copper coins extant after demonetisation, for the early years, such as George IV's reign - the readily available high grade copper specimens gradually increasing for subsequent years up to 1859, which would have had only 10 years circulation at the end of 1869.This is based on an assumption, as you rightly point out, that they weren't too high up on the average coin collector's priorities at that time, and hence not too many early high grade examples hanging around in collections.
The ones that did turn up being down to random chance findings of coins equally randomly deposited in various places.