First of all, I am very sorry for your loss.
I hope your vet can help to identify the cause of death. Unfortuantely, freezing the snake might have eliminted the ability to do a necropsy (reptile autopsy). Let's hope you never have to figure out a cause of death in the future, but if you do, just put the snake in a ziploc and put it in the fridge, not the freezer and then get it to a vet ASAP.
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