Every time my three-year-old bashes the keyboard randomly my hot corners stop working. What key combo is she pressing? Whenever I make the mistake and leave my MBP unattended and unlocked for more than a minute, my three-year-old rushes in and starts randomly mashing keys on the keyboard, pretending to type.  Every time, without fail, afterward, things seem OK but the hot corners no longer work and the Dock (which I normally have set to auto-hide) will not rise up from the bottom of the screen when hovering there; I must click the mouse at the bottom of the screen, where the Dock is hiding, in order to make it rise.  Merely hovering, like usual, does not make the Dock rise.

What key combination is she pressing to trigger this behavior?  And how can I turn it off without having to completely restart the computer?
You can search through the keyboard shortcuts with System Preferences -> Keyboard -> Shortcuts.

For me, "Turn Dock Hiding On/Off" is Option ⌥ Command ⌘ D

I don't see a keyboard shortcut for enabling/disabling Hot Corners (in High Sierra), though maybe your list is different?