OMG, I am so sorry - as I was reading I kept thinking, "I hope it wasnt day lilies" cos I knew youd be feeling what I felt when my boy ate day lilies and I had to rush him to ER. He was saved only because I happened to read a story similar to yours..... AND I happened to see my boy munching on them so was able to get him to ER in time. I had dug up and moved them out of his catio, but STUPIDLY had forgotten to remove one.
WHY there continues to be such ignorance about this - I dont know. Ive been at garden centers and I tell people there you really need to have warnings on these plants that you are selling - they can kill a cat. And these people- they just look at me stupidly like I have two heads. I say, please look it up on the internet if you dont believe me. And they say yeah, sure, we will. But I go back and they havent done a dang thing about posting any warnings.
Please, please, take good care and someday find forgiveness for yourself. You did your absolute best and know that Bear loved his life and he loved you his human dearly.
All plants should come with toxicity warnings for people and animals. It's unfathomable to me that they aren't!