It's an iOS bug. It happens now and then for me, and when it happens it drains all the battery juice. Still no fix to this date.
This is like blaming people for not locking their door after they’ve been robbed. Yeah, they should have locked their door. But the person who actually did wrong is the person who robbed them.
Blaming somebody for not taking extra steps to reduce the chances of something happening to them that is ultimately the fault of another party is not right.
Our society has elements that will harm us. It is up to us to take action to reduce the likelihood of that happening.
How did you determine it's an iOS bug?