I found a small black shiny insect in my house...what is it?

I just found a small black shiny beetle like thing in my house. At first I was sure it was a tick, but then I looked up pictures and realized that ticks are not black and shiny. It was crawling on my carpet near a dog we are dog sitting. It was flat, and looked like a tick...but it was smooth, black and almost like a metalic shinyness to it. I tried to smash it with toilet paper and it wouldn't die/smash, so I flushed it. Wierd that it wouldn't just die. What could this thing be?