He probably didn't trust your documentation because you could have doctored it. I was educating an Ohio LEO once with a copy of The Condensed Guide To Ohio Concealed Carry Laws when he noticed the name on the front and realized I was the author. He gave me a really strange, distrustful look until I pointed out that everything in the guide had links to the Ohio web site where the actual statutes were and called up a couple of those links for him to see. Cops deal with so many dishonest people on a daily basis, all day long, that it's hard for them not to be distrustful of people they meet in day to day encounters. It gets ingrained into them after a while.