Tore my 2013 LTZ down to the head gasket. Coolant had flooded the spark plugs, coolant in the oil, and there was a massive internal water leak (ended up in the oil). Long story short, the car had been driven without a cap on the coolant reservoir after service was done on it (shop refuses responsibility, but I'm already taking steps to be reimbursed). It overheated for a matter of seconds, but wouldn't start again.
The head gasket appeared to be fine, but I will still be taking the head in to get checked. Is there anything else that could have caused all of these issues, or should I still assume the head gasket, despite it looking okay? Pics attached of before and after the head gasket was actually taken off.