firestone rancho bernardo Firestone complete autocare forgot to put cap back on reservoir after radiator flush. car overheated, blown head haskets. san diego California

 took car in for radiator flush.  Took car back, and that night my civic overheated.  two days later car overheated again.  Checked under hood.  There was no cap on coolant reservoir!  There was coolant almost up to the brim and bubbles were surfacing.  if the cap had been blown off by pressure - as firestone kept saying - there would have been coolant everywhere.  There wasn't.  called firestone and took it in per instructions.  Comes back blown head gaskets.  went through their shady claims process, and basically they are calling me a liar in the end.  They're only defense is that they don't have proof that the cap was not put back on after service.  its been almost two months now.  Now my car is complete garbage, and I ride a skateboard to work - takes three hours.  Im on the verge of seeking a polygraph test, and if they don't honor it through their claims dept, I will be seeing them in court.  I really hate firestone - they've made an enemy for life with their lack of honesty and integrity.