The switch cover in question would have a copper wire threaded through two holes. This thin gauge wire means that it should not be able to be operated by error. If the wire locking was done by a special set of pliers it should not be able to be undone and redone without anyone noticing, If however it had been done by hand which is a more probable way of doing it, it could be undone and redone afterwards. Hopefully the crew should have noticed this.
Hope that helps.