2012 SUBARU WRX Engine Problems

I HAD CHECKED MY OIL ABOUT A WEEK PRIOR TO THIS HAPPENING. I WAS OUT ON THE INTERSTATE ON MY WAY TO GET MY OIL CHANGED WHEN I HEARD A LOUD KNOCKING AND LOST ALL POWER STEERING AND POWER BRAKES. ALMOST CAUSED AN ACCIDENT ON THE INTERSTATE. I HAD IT TOWED TO A MECHANIC WHO TOLD ME ALL OF MY FULL SYNTHETIC OIL WAS GONE FROM THE ENGINE AND IT WAS BLOWN. THERE WAS NO SMOKING NO LEAKING NO LIGHTS OR ANYTHING TO LET ME KNOW SOMETHING WAS GOING WRONG UNTIL IT WAS TOO LATE. SUBARU HAS BEEN ARGUING WITH ME FOR MONTHS AND FINALLY SAID THEY WOULD COVER HALF OF THE REPAIRS BUT I DO NOT FEEL I AM RESPONSIBLE AT ALL. I SHOWED MY MAINTENANCE RECORDS TO A SUBARU ENGINEER WHO SAID IT WOULD BE NO PROBLEM GETTING THE ENGINE FIXED AT NO COST TO ME. WELL APPARENTLY...