My condolences on your troubles. Not making light of your issues, rather trying to get to the real bottom of what may have happened if they did put in a proper antifreeze mix refill.
I will throw this out there as a possibility.
I work with industrial UV lighting which creates enormous heat. The systems are all water cooled. The customers never take care of the chiller units until something clogs up, and then we have to do a chemical flush to get out all the crap.
When we come at the system on day one of the flush, nothing is moving in the pipes, but nothing is leaking. Then we start to dissolve the junk clogging up the lines with the flushing agents.
Lo and Behold! The only thing stopping that rotted out coolant channel from leaking....wait for it.... WAS the junk in the system!
Now that we have removed the junk, the hole starts spewing antifreeze.
Who is to blame in this situation? Whoever originally let the system go this bad.
I've been on the other end of this dilemma and it sucks for both parties.
RICE - ITS WHATS FOR DINNER !
Lots of V8 SHO's