MacOS – Why did MacBook Pro Touch ID stop working temporarily

The same thing happens to me in 10.9. I also tried changing require password to wake of security preferences and putting displays to sleep instead of starting a screen saver:

tell application "System Events"
    set require password to wake of security preferences to true
    --start screen saver "Random"
    do shell script "pmset displaysleepnow"
    delay 5
    set require password to wake of security preferences to false
end tell

Neither of them helped though.

You might log out to the fast user switching screen instead of locking the screen though:

/System/Library/CoreServices/Menu\ Extras/User.menu/Contents/Resources/CGSession -suspend

Maybe it was an SMC reset:

Resetting the SMC on portables with a battery you should not remove on your own

Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
6. Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.