Oh Katie, what a horrible accident to have happened. No matter how many people mention that "IT ISN'T YOUR FAULT", you will still blame yourself. I'm happy that he is home with you even if it's just for a night. I know this is what you both need at the moment and that he ate a little bit.
Big time prayers on the way for precious Andy and {{{{{{{HUGS}}}}}}} for you. Just think if you had decided to go outside or to the store, the outcome would have been tragic. BUT, thankfully you were home and saved him from a certain death.
Years ago, when I went into the fridge to get a drink, I didn't notice when I closed the door that Mooky had jumped into it. About 5 minutes later, the hubby went to get something out of the fridge and out popped Mooky. Thankfully he was okay, but I dreaded the thought of how long he would have been in there if it wasn't for the hubby opening the fridge up.
Another time, my sweet Katie girl, got closed in my sons closet in the morning and was closed in there for the whole day while everyone was at work. When my son came home, he could hear something in the closet so opened it up and out came Katie giving him heck like you wouldn't believe.
It's unfortunate that these things happen, but they are "ACCIDENTS", that can happen to the best of us. So please dear sweet girl, do not beat yourself up over this, okay.