I've broken a brand new keycap in the past on an MS surface 2 - just typing too, it can happen.I swear I just type normally.
The clips that hold the keycaps to the scissor mechanism are unbelievably tiny. Easy to get a rare faulty part that slips though QC, I'm sure. Still annoying, but hopefully not an ongoing issue
From your OP, the picture looks to show the clips at the top of the keycap have snapped, or the part of the scissor mechanism the keycap clips on to has snapped. The switch itself is probably probably fine... I'm guessing if you poke it, you still get the .
The 48hrs from Apple sounds like typical Apple Store BS... Either you need an whole new machine (the entire keyboard is riveted to the unibody), or they're just going to clip a new key, and/or scissor mechanism in place.