Transfer case on Chevy S10 pickup

My 2001 Chevy S10 pickup was making grinding noise in 4 wheel drive. Took the truck to a repair center. They replaced the transfer case. Within 3 weeks all of the transmission fluid had leaked out. Had truck towed to 2nd repair center. They took apart transfer case and said a gasket had not been installed and first merchant had tried to use RTV as a sealant instead of replacing the gasket. First merchant says what they did has nothing to do with the transmission leaking, but now that the 2nd service center replaced the gasket and reinstalled the transfer case nothing is leaking. How do the transfer case and transmission interact in a way that repairing the transfer case would cause the transmission to drain of fluid?

The transfer case is mounted to the rear of the transmission. So when filling the transmission with fluid you also fill the transfer case with fluid. If there’s a leak at this connection the transmission will leak all it’s fluid out.

Tester