What makes you think that the GA would bother to do that, risking his/her job in the process? What makes you think the GA and the luggage people are both willing to knowingly scheme against your mother's bag? It doesn't make sense.

As the other poster already mentioned, the cables sent with the tags tend to easily become undone. Absent any specific proof, there is no reason to assume both the GA and the luggage handlers are engaged in a conspiracy to steal.