Frustrated!

So I got my head gaskets replaced by McCurley Integrity Subaru for $1,800. Fine and Dandy. Head gaskets shouldn't go out at 68K miles. So I am a little frustrated. I am the person that does all maintenance to their car when needed and I take care of my car so it will last. Well, I am mad that due to having the coolant flushed at another place....Firestone......it was done incorrectly not adding the special conditioner to the antifreeze in order not to have the head gasket problem. Firestone said they would take care of it (pay me back for McCurley to fix) but now they are needing all this proof that really doesn't happen, i.e. Lab Results for coolant testing. They have print outs that say specifically that if the conditioner does not get put in with the antifreeze that it corrodes and makes the head gaskets rub...causing them to leak oil into the cooling system. Which in my case happened and had to have the head gaskets replaced. Oh this is soooooo ridiculous. Obviously they know they are in the wrong but are being absolutely idiotic. UGH! So that is my fun fact for the day.