Actually, since it's a DVR storing to a hard drive, you might be able to recover the recording, much like recovering deleted files in Windows i.e. Google [dvr recover deleted recording]. From those search results it looks like some devices/providers even provide a trash/recycle bin.

Unfortunately, that's not an option with our current DVR, but I'm looking into another one, thanks.

Given that KC won yesterday to go 7-0, I gave the guilty party an executive pardon. But my mother-in-law better not do it again. :)