Sara,
If your account is a margin account, then you can be certain that your shares are in the brokerage inventory and available for shorting. They were probably shorted the minute you made your purchase.
If you have a cash account it is very likely that your shares are in the brokerage inventory and available for shorting. They were probably shorted the minute you made your purchase.
Calling your broker is recommended, but when you opened your account you signed an agreement that allows them to loan your shares as they see fit without notice or compensation.
The only way to insure that your shares are unavailable for shorting is to call for the certs, If you have any trouble getting them let everyone know.
The Bird of Prey