You can exploit the behavior of the "built-in" %device%
variable here. Normally, this refers to the name of the triggering device. "Wait for event" will set this variable to "timeout" if the wait ended because of the timeout rather than the actual event (or to the device name in the other case), so after your Wait you could do something like:
Set myLocalVariable to %device%
IF (myLocalVariable equals "timeout") THEN
Off: Garage Light
END-IF
You'll need to create a local string variable in this rule (or use a hub variable if you really need to), since you can't directly access %device%
in the way you'd need to without this workaround. Otherwise, it looks like that should do what you want!