Wait . . . what?
What constitutes "using their key absent-mindedly"?
In the cases I've run across, mostly here on this forum, people have inserted the tip of the key into the battery-charging input port instead of the keyway, since they're on the same side and I suppose relatively close to each other (?) - not sure about the latter, don't have one to look at in person.
Instantly, the key shorts out positive to negative in the battery, a spark or twenty ensue and the internal fuse (at a minimum) blows, rendering the battery 4-paws-up. At that point, the fuse changeout varies from one internal design to another but a big hassle at a minimum.
I don't know how one would stick the key into the charging port if the protective weather cover is in place - maybe they get loose, pop out, or fall off. Also, since the key no longer provides a useful service like disconnecting battery power from the bike, I'm not sure why one would even need the key to ride (or steal) the bike unless installing or removing the battery itself.
As a recovering mechanical engineer, I consider this the user's fault with a heavy contributing percentage the fault of idiot designers for even making such an egregious error possible from simple absentmindedness.
So, be careful out there if you have one of the new semi-submerged battery designs on your bike.