My car is now going through the exact same issue as OP, currently at Toyota having the compression test done. I own a 2013 Scion FRS with 27,000 miles. I had my oil changed last Friday along with my transmission fluid and differential fluid. Noticed the car was running really hot, about 210 degrees at its peak. Checked my coolant, overflow was bone dry. I picked up Toyota blue coolant and filled the radiator up first, it only took maybe a cup of coolant. Then I filled up the overflow to a few inches past low, drove my car around for a little, temps were back to normal. Woke up this morning, checked my coolant, pretty much bone dry. Dropped the car off this morning at Toyota and they just called me asking if I had any other information and that there was no leak and now they were going to run a compression test. They also told me that my differential plug was as they put it "finger loose" and differential fluid had sprayed all over the bottom of the car. Not going to name the shop that did the work because I want to talk with them about this first but that was just really disappointing to hear. So definitely freaking out a bit now, specially after reading how much just the parts cost for OP. My main concern is my warranty is technically still valid through 30,000 miles but I have an OFH and Tablet tune on the car.
