A baby beat me up

Recently my neighbors were away for a while and I was charged with looking after their kid at their house. First let me make it clear that I am an adult male of average height and a slightly heavy build.
I arrived relatively early in the morning for my duty, which was to keep tabs on my neighbors' 2-year-old girl Cassandra. I knew her from before and she always seemed like a really sweet kid, so naturally I had no idea what was in store for me.
Anyway, for a while she was playing while I was sitting on the couch a few feet away watching soap operas and going over my stamp collection (it's a nice stamp collection). Things were going smoothly until lunch time rolled around. I picked Cassandra up out of her play pen and carried her into the kitchen to go over what was there. This is where things get interesting.
In assessing the available munchies, Cassandra and I got into a heated altercation regarding who would get the last Pop-Tart. One thing led to another, and before I knew it, I was on the ground with a screaming toddler sitting on my chest and bashing away at my face with her tiny fists. I started bleeding, and I attempted to retaliate by slapping her. She quickly shook off the attack, let out a horrific screech, and then grabbed me by my ears and began beating my head into the kitchen tile. After a bit of struggling, I was finally able to wrestle her off me and then frantically began to crawl to the living room where the phone was so I could call her mother. I was almost to the phone when Cassandra came up behind me and hit me over the back of my head with a heavy ashtray, causing me to fall flat on my face. She then crawled over my back, grabbed the phone, and tore it from the wall. That was the last thing I saw before I lost consciousness.
I later woke up to find her sitting and playing as if nothing happened, a very empty Pop-Tart wrapper beside her. Later her parents returned and naturally asked me what happened in regards to my battered appearance. I was horribly embarrassed so I just told them that I walked into a door. The deal with the phone I blamed on a ghost.

I've just been so angry, so embarrassed, so humiliated since then that I can hardly think straight. Just the other day my neighbors got a hold of me to ask if I wanted to babysit again, and to be honest, I just don't know what to tell them. I simply can't tell them what happened and I'm honestly scared to see Cassandra again for fear of what she might do. This is messed up.

Has anyone else been in a similar situation?
Do you think I could have handled it better?
Should I attempt to get revenge?

Please help.