Did it unscrew itself magically?
As either type of keypad that fit on this have a retaining screw as well as clips.
As mentioned if the "Spanner" is lit you need the engineers code. Was it fitted by a company or a friend as either on has left it on engineer reset for tamper on purpose, or the other did not read the latter commands in the manual :D
Probably the most robust little panel of its type, they don`t just fall apart.
Alarm, November 2012