Caliper leak!

When buying this PP and doing the check out, I thought I noticed something a little strange. Both front wheels had a trace of something on the inside. I assumed maybe it had been driven through a pot hole and something splashed on the backing plates and dripped down. I always detail a new vehicle and when I pulled the wheels to wax inside and out, I cleaned off what looked like a small oily, dirty line. A hundred or so miles later, I noticed it had returned on the driver's side. Got worse, so pulled the wheel and then I could see the source. Got it in to a dealer and they replaced the whole caliper sub-assembly. Wanted to send it in for analysis.
I suspect why both front wheels showed the leak was that maybe the detailer at the dealership had pulled both front wheels when working on some water spots and got them swapped going back on.