I don't own an Okanagan, but I might be able to give some ideas.
I would start in the sink cabinet, deep into the left side there might be a hole or access that runs in back of the shower stall.
Looking at the floorplan, in looks like there are empty areas back there where the shower seats are formed.
Your fresh water fill is on that outside wall no?
Is there a access panel on the base of the shower enclosure, that you can see into, and locate the fill hose?
Or worse case, pull the outside hose bib out to see if the clamp came loose.
Good Luck
Rick
