Hi Gary,
Darn Engineers, They never get to repair or deal with their creations. It is difficult at best trying to determine where the water is coming from. Once it dries out, cover the shower drain inside with something that will allow you to fill the shower pan about 1 inch. Observe from the outside access while someone removes the shower drain cover you fabricated. It is not uncommon for the putty between the pan and drain to dry out and crumble when the coach is 16 years old. If that is the case, you'll see water leaking above the p-trap. Another source on older coaches is the cone washer on the shower fixture on tha "hot side" . Constant temperature changes on the cone washer compromises the seal over time.
Regards, Fred