Police Knife Seat

I stopped to help someone on side road and ended up getting arrested for 1st degree felony aggravated robbery the police officer never took a statement from me whats with that I spent 4 months in county jail awaiting trial and would be there today if not bailed out? I have turned myself in and all and currently waiting on trial the story is I stopped to help to what appeared flat tire they jumped in my passenger door grabbed my pocket knife out seat and tried to kill me and when called police when they showed up he asked the two guys something and when he came to me asked me if that was my knife I said yes he then said put your hands behind your back you are under arrest for aggravated robbery and that was it. I did hear when the other two where giving there statement they said they took the knife out my hands. Well back up couple years I am am ex military and served as infantry in Iraq. Also one the guys who made statement was arrested 6 hours later and was peppered sprayed