Im not sure what they are selling at your plant store...Maybe someone there got seed for the Mojito. I had to get mine from Canada. Richter Herbs.
http://www.richters.com/Web_store/we...?product=X4025
The real Mojito is from Cuba. I checked and I see the plant for sale on Amazon. It is still fairly rare here in the U.S. Possibly someone at your store has gotten some of the original Mojito and is propagating it?