Truth be told, he couldn't have eaten it. If you saw it, it was enough to seriously hurt him. It had to be something else. I used to work at an emergency clinic. I have seen so many animals come in because of rat poison. It is so sad. Most don't make it, the others leave with permenant damage and thousands of dollars in medical bills. So rest easy, you did nothing wrong, that couldn't have been poison. However, if you ever see anything like that again, get a sample and find out what it is. If it is bad, and could hurt your dog, you have to find out right away. The quicker he gets treated, the better his chances!