Hi CapnSteve59,
From the subject line, it sounds like you suspect the water heater has been bypassed for winterization and you don't know where the bypass valves are located.
On trailers that have a Universal Docking Bay (UDC), there's typically a bypass valve there. If no UDC, there are usually 3 valves on the inside, close to the water heater. I've attached a picture of how it looks on a Cyclone. Yours may be similar.
The open question is how to access. On some rigs, there's an access panel inside. On others, you have to take down the rear basement storage wall near the water heater. Usually the dealer shows you this during the PDI walk through, but sometimes things can get skipped.
Perhaps another Silverado owner will chime in with how it's accessed on theirs.