Coho, among other fish, are known to swim after your lure and strike it downstream from where they were holding. The fish may have bitten the body, with the hook trailing outside its mouth, then once the take was felt, the strike was made thrusting the hook in from the outside. I've seen hooks outside with spinners, spoons, flies, roe. Especially with a longer bodied presentation, such as a spoon where the body is long and the hook(siwash) is long. The fish didn't bite the hook, it bit the spinner. There just happened to be a hook at the end of it.
Nice fish BC.