Oldsmobile Questions? Ask a Mechanic for Answers ASAP
My advice to you is if the vehicle has been flooded, any module within the vehicle that went under water will be damaged, and probably the cause of your battery drain.
More than likely the vehicle doesn't start, and if the garages scan tool depowers itself then there is a fairly major power/communication issue.
All the modules need to disconnected to see if the battery drain disappears.
Then start with the BCM or whichever is the bus master, and see if it works on it's own.
Generally any vehicle built after 2000 is an insurance write off after being flooded.
Hope this helps you make a decision of what to do next.