That definitely looks like a deformity of some sort. At this stage, it is done developing its limbs, I would think. If you let it go, it might live for a while, but Mother Nature is not usually kind to any living thing that has a defect. I am also one of the biggest saps on the planet, and if I had found it, I would probably keep it. It's quality of life is going to be 100 times better with you and your girlfriend....besides, look at that little face...