I work in the claims department for a Top 5 auto insurer and it's bullshit that no fault accidents don't exist. If you didn't have your key in the ignition and the other guy backed into you, no one would try to argue you even had partial liability.
That being said, in order to pay out of third party coverage (liability) a company will take the word of its policyholder unless there is a witness or overwhelming conflicting evidence. Think of how pissed you would have been if the other guy's car was fully covered under your 3rd party coverage. Also since the other policyholder was found 50 percent at fault, in most states you would only owe 50 percent of your deductible. Not sure if your deductible is $1000 but if you paid your full deductible you might be owed half of it back.
USAA actually has the highest customer satisfaction rates out of all the auto insurance companies so those who qualify for it usually stick with it. Of course paying 250%+ of your prior premium is outrageous so I'd consider shopping around (perhaps to my company
).