Prius recall 2019

I took my Prius in for the recent recall work. Everything was good but I received a call from the dealer saying that they needed to do another check on my car after they completed the work can I bring my car back to them. I did as they asked, and they said everything was good. My problem is that the next day my car had a bad order. Because I often have my dog in the car I thought it was the dog. I cleaned out my car and vacuumed it out. Order still there, so then I shampooed everything. No help! I ask my husband if maybe an animal could crawl up in where my spare is and maybe died. I ended up taking everything out and found some black fluid around my tire. Horrible smell! Where would that have come from? To thin for oil. Could it be from my battery that is back there?