To be honest I stopped using warm water for thawing as it also washes away the rodent's smell / odour .
As I understand it , many ( all ?) snakes use their tongues to smell/taste their prey so that's why I changed ( very successfully ) to heating with a hairdryer after thawing on either a heat mat or radiator or boiler or whatever kind of heat source ( be care not to cook the rat though - just warm enough to thaw ) .