Cats lower jaws have a "seam" right down the front, it is a favourite area for most facial fractures, you may also notice his two center, lower front teeth have a gap, that to me would indicate a mandibular fracture. My own moglet got trampled by my horse at a flat out gallop last year and had bad head injuries.......but she was kept in a dog cage in my empty stable and kept dark for two days and she made a brilliant recovery, with some help from a retired vet who does a bit of locum-ing who helped me set up the drip. He obviously feels happy to come "home" which is why he's back with you, it just took him that while to recover enough to start his "Incredible Journey" back to the fold.