Maybe it was the dog? From 5 Facts About Flatulence In Dogs (and Cats) You Need To Know:
“It happens. Smelly emissions of intestinal gas that may have you wondering if there is a pile of something to clean up. While the joke is to “blame the dog,” cats may also experience flatulence.
Is gas a health problem? Usually not, but here are 5 things you would know about flatulence in pets, and if it is something to be concerned about.”
5 Facts About Flatulence In Dogs (and Cats) You Need To Know. It covers various causes of gas in your pet as well as ways to help gassy pets.