Hello,
I found the position of the golden egg, Unfortunately at my main game line. Before this patch I knock down the nest and the egg is not in it.
For all other game lines, where is nest on tree is golden egg in nest.
Can I solve it so I have an egg for my main game line?
Not sure which nest you talk about, but I was guessing it should have been in on specific nest, but only one groschen for me there 
Anyway, is there any special use for those eggs after?
Also, it seems to be no specific usage for the weapon?
Egg is on specific place on specific nest (SPOILER) its in nest near Rattay church near alchmey store. I shot down nest on beggining this main line… and now is nest on ground… but nest is empty but my other game lines have golden egg inside…
PS: golden Egg activate hiden perk
The nest was untouch for me earlier, but no egg there…
I too have one playline with no golden egg. Yet it is there on others. For some people the weapon is missing from the chest, but the egg is in the nest. It just seems the whole event is buggy.
Bugged for me as well, sadly cant find it there as well. 
I start to think that it may be few potential location for this one.
Looking around for some other nest.
I found a green one outside Rattay for example.
I travel around all nests on map and I found only one golden egg