The Missing Arrow

One of the landmarks along Mexico City's Paseo de la Reforma is a fountain featuring a statue of Diana, the Roman goddess of the hunt.  

The fountain was erected in 1942 during the Presidency of Manuel Avila Camacho.  The nude statue of the goddess provoked one of the most laughable controversies in the city's history.  Conservative elements, including the League of Decency, were scandalized by the nudity.  One of the members of the League was the wife of Avila Camacho, and the sculptor gave in to the pressure.  He cast a pair of bronze panties to put on the statue.  However, he astutely foresaw a less prudish future and soldered the metal clothing to the statue in only three points so that it could be easily removed.

Finally in 1967, the mayor of Mexico City ordered the panties to be removed.  However, the statue was damaged in the process, and a new statue was cast from the original mold.

I bring this up because a couple of weeks ago I saw something I had never noticed before.  Just across the street from the fountain, between the entrances to a bar and the Cine Diana (a movie theater named after the fountain) is an arrow is stuck into the wall with this plaque beneath it.

     The plaque says...

The Arrow of Diana the Huntress

It was believed lost

and was only hidden

reserving its good luck

for whomever asks for a wish here.

If you look at the photo of the fountain above, you will see that, indeed, Diana has a bow but no arrow.  I am skeptical as to whether or not this arrow really belonged to the statue, and if so, how was it lost and where was it found?