Buddy of mine got ticketed for not having his license on him while we were trout fishing. The warden was pretty forthright in saying that if he actually had a license to send a copy to the court with a letter explaining the circumstances, and the ticket would be voided. He did, and it was.

Now, we weren't steelhead or salmon fishing, and the rules are pretty strict about having your tag on you. Seems to me that if one's tag was 'in the truck', that that could be used as a nice excuse to just carry your fish up to the truck and put it away without tagging it. Not saying that's what your friend was doing, but that may have been how the officer looked at it.