It is possible to bring it home on a new animal that is infected and from there spread it around. That's why quarantining new animals is so important. Also frogs sometimes have a tendency to sit in the same spot a lot and deficate there as well. So if the frog is sitting in its own excriment all the time it is likely that it can come down with the disease.
So in the future quarantine all new frogs (or other animals) before introducing to an already established population. Also keep a sharp eye out for feces, escially if your frog isn't all that active.