If you don't have any of the powder...Try holding a slightly moist tea bag to his little toenail. I know this sounds crazy but years ago when I worked in a dental office we recommended this for anyone who had an extraction if it was still bleeding after they removed the gauze we put in initially. It will help clot the blood and it is soothing. Just hold him on your lap and hold it to the bleeding toenail for a few minutes. Hope he's better by tomorrow.
I'm with you I'd be really, really upset especially since they didn't tell you and there's no way they didn't know when they did it.