Chain Length

I've been a competent bike mechanic for a few years. And yet, sometimes I make really dumb mistakes. Fortunately, (or unfortunatly, depending how you look at it) most of the time they occur on my own bike. Long story short, Aaron, Art and I went riding this morning. Less than 50 yards into the ride, I shifted into my big cog. No big deal right? Right, unless you are running a 1x9 and put a bigger chainring on your bike the day before, and spaced checking chain length. If that doesn't make sense, here's the simple explanation. My chain was to short and this happened:
When that happens, your bike doesn't work. Which is the pits when you're only 50 yards into a ride. (Especially when you've already spent 15 minutes nursing wounds- right Aaron?, and another half hour fixing tubeless setups, -right Arthur?) Oh well I ran back to the shop and snagged the demo Nine Solo and we got our ride in. And it was a good one.