Your story was an interesting read. I've been lurking here for awhile. I am a complete newbie at tree climbing, but I am getting into it for just the reason you described -- to help return wayward birds of prey to their nests. I volunteer at the International Center for Birds of Prey near Charleston, SC. We deal with this situation a number of times from the late winter to early summer, and tree climbing would definitely help in some situations.
Some quick notes on your story, some people who could have helped you out with advice (especially with getting George out of the bag without having to shake him!) is the the Carolina Raptor Center, located just outside of Charlotte. They are a great organization, and I'm sure would have helped and probably even offered to look George over to make sure he was alright prior to putting him back. I also mention them, because we are always in need of people to help put chicks back in nests (hence the need for me to learn tree climbing), so if you are interested in more adventures like this (but with more gear, and a little bird handling training), you might want to contact them and see if they have any volunteer openings for tree climbers.
Good job, and thanks for helping the Owls!