I was thinking the same as Aminah, if you have an autopsy made for poor Darcy and determine that the grit or whatever rock was in the seed killed your lovely keet then you should sue. Not because any money in the world will make you feel better about Darcy's death, but because they HAVE TO PAY for THEIR MISTAKE, so careless these big companies are
Although I am relatively new to the forum, my thoughts are out to you and your Darcy. It's good you were with him in the end. I'm sorry for your loss.