Just because the hook ended up on the outside of the mouth, doesnt mean the fish "didnt voluntarily take the lure into its mouth" which is the way the fishing rule/reg book states.
I fish with spinners/spoons probably 60-70% of the time while river fishing, and have hooked several in this manner. I used to rig a small bead chain behind the spinner with the hook attached aft of it. It increased my rate of landing fished which were hooked (many of which inside the mouth) but also increased the times the hook was on the outside of the mouth, I also fish exclusively the siwash style single hooks on my hardware. I have since stopped the bead chain rig and gone to a smaller hook (size 1 hook/ size 4 spinner) and this "problem" is less frequent.
Tight Lines
RL
aka Dew