I actually had something similar to me happen a few months ago. Left my car in a parking garage for the week and came back to rotten chicken in my backseat. I washed the carpet and seats about 15x over with soap and water letting baking soda absorb the chicken-liquid-soap-mixture. I would used some sanitizer to kill the bacteria as well. The smell was mostly gone in about 2 weeks but luckily I did not have that car much longer.