Batteries can fail without any early warnings, especially these AGM batteries. For me, they usually start the bike fine at home just fine. Stop at a gas station or run an errand, click, click, click goes the starter solenoid and then you're stranded. Your issue sounds a lot like that an internal connection bar was cracked making intermittent connections and then separated completely momentarily and you lost power.
I've never had this happen. Haven't seen it on the boards either as a common problem. It was probably an internal short in the battery, due to poor manufacturing. When you say that the charging system is okay, I assume you used a voltage meter to measure voltage with engine off (~12v) and voltage with engine running (~14v). Yes, the FI will shutoff at low voltage since it is an electronic system and needs ~12v to operate normally.
I had ridden to Gardiner, MT, on my way to Hyder, Alaska, when I thought my battery on my Concours had died. There was no battery in Gardiner -- the nearest was in Livingston. I started fiddling around and it turned out the cable to the battery ground was loose. I tightened it up and used that battery another 2-3 years. The old men at the campground office were really impressed -- they thought that I must be a terrific motorcycle mechanic. Fooled 'em.