Unless something the guy did caused (or allowed) the wind to lift the thing, he is not negligent. No negligence equals no liability.
I guess what I'm saying is it sure seems like a quick review of the relevant tent info and AZ law suggests that the fact that the thing blew away on its face shows negligence. It's a garage sized kite for goodness sakes, its use, even more so than any walled tent is inherently unstable and somewhat dangerous. The erector and user of such tents have care duties. Its on the label and the directions.
As to the testimony of the blown away tent guys friends:
Are these party-goers knot experts... what do they know? Who are they to testify or not testify as to the soundness of the tie job.
Is there some proof that this guy took reasonable care given the risks involve in using a tent. I don't think so. The poster did not make this clear, but this was a tent camping jamboree type thing... was only his tent blown down? Did similar awnings hold up?
The weather service will have data on the wind. How much wind is a tent supposed to withstand before when it blows free from its moorings is it negligence? And how windy is it to be totally out of human hands?
This is why I would suggest that the poster should pursue a small claims action for his valuable tents and property, with or without the testimony.