To bring your touchpad back to life, enter the following command into terminal:

The key "/desktop/gnome/peripherals/touchpad/touchpad_enabled" is where gnome-settings-daemon remembers that you disabled your touchpad. This is the reason, why it is disabled even after a reboot.

The issue will re-appear, next time you disable your touchpad. You need to prevent gnome-settings-daemon from disabling your touchpad in the first place, because the Synaptics touchpad driver does this already. To do so, run the following command in a terminal:

This dissociates the key to lock your touchpad from gnome-settings-daemon. If for any reason, the latter command breaks the lock touchpad support for you, than you probably have a different issue. To re-associate the key with gnome-settings-daemon, run this command: