What DID happen in the meantime?

My aunt called to ask for some help with some research. She gave me two different problems from two different branches of her family. One was fairly easy. The other, I'm still struggling to find out anything beyond what she has given me.

She said that some of these lines, especially the hard to find one, has records once you go back far enough. Not only are the records there but they are in excellent condition and contain tons of information. Then there is a black hole in information available. Then the records pick up again. So what happened in the meantime?

Some of the standard answers are:

• Fire
• Flood
• War
• Ran away from home and changed names
• Adopted when parents died/ran off/couldn't afford to keep them
• Moved to frontier

And the most popular of all:

• Poor record keeping all around for whatever reason.

I wonder what the answer will be this time?