I'll take you at your word and the only possibly annoying nag I'll state is this: Keep a spare tank on hand!
The only real apparatus to prevent leaks is between your ears and developing the pedantic habit of close attention to detail every time to so much as touch your system. I dunno if you're using traditional lines or EVABarrier, but if the latter, though most folk who use it (myself included) love it, I have had it leak when I've bent the hose at the connector 'too much', even with the little blue retainer clips installed. No system is completely perfect, so we need to test every keg, line, tap and junction every we use them. I learned that both from my first 2 gas leaks and, like you, a loose post which amazingly did not leak (or at least not very much) until the keg had kicked and I discovered it while cleaning.
Just curious though; Can you post pics of your system, even though that means a lot of us will annoy you by filling this thread with stuff you already know, but just maybe when you trace the problem we'll all have a clearer picture of things to watch out for ourselves?
Sorry about your lost gas, hope you can get a replacement soon.