I was wondering....... I've had my bike for 2 years - it's a Gary Fisher Nirvana.

I'm wondering if my frame is a "kids frame"??? Under the handlebars, on the frame, it says "13".
I just looked at the Gary Fisher website, and saw the following sizes for the Nirvana:
SM (15.5") | MD (17.5") | LG (19") | XL (21") |

I am short (5'2"). I'm wondering if I was sold a kids frame without being told that it is a kids frame??
Perhaps it doesn't make any difference??

I've just recently started riding earlier this month, (Thank you God...no more parking lots, either)!!!, which is why I'm asking.
I've had my bike in storage for a couple of years b/c I didn't like riding in traffic.....

Any thoughts would be appreciated.

Thanks!

Denise