Oh dear Lord!! My heart is aching for you right now. I am so terribly sorry. Don't blame yourself like that. You did not know.
Our neighbor had a sego palm and he had a Vizsla. I mentioned to him about the dangers of that palm and he got rid of it. Now I always keep my eyes open to see if anyone else has a sego palm and a dog. I will let them know how poisionus that palm is. It's my nosy duty!