|1- Check touchpad features for options. Sometimes a hidden combination of keys will turn on or off a feature and that is what happened to yours.|
2- Try restarting the laptop. Sometimes that is all that is needed to 'fix' things.
3- Try reinstalling the touchpad's driver from the machine mfg's website.
(use a USB mouse if you have important things to do until you get it working right again.)
You have to be a little bit crazy to keep you from going insane.