There's a post on another RV forum that
shows the water pump switch on the same panel that shows the tank levels, 120VAC line voltage, tank levels, etc.
In that photo it's a green switch to the left of the red generator switch.
Given that it's pretty clearly labeled and you didn't see it, it's possible that someone has rewired your coach and moved the switch. Or maybe they took out the pump completely because they never used it. The panel in his picture has the Dynasty logo on it, so it's probably the original panel, but yours might not be.