Code 1235 Foreign Object on RF Wheel Sensor - Anyone Experienced This?

Sorry to post this here since the issue happened on my v, and I posted it over there, and the problem is fixed, but the main question went unanswered: has anyone else had this happen?

"This morning my 2012 Prius v's ABS, Skid Control and Tire Pressure indicators all came on at once and would not reset with a restart. I took the car to a dealer who diagnosed "C1235 Foreign Object on RF Wheel Sensor". They removed the right front Hub Bearing and found a thin piece of metal attached to the speed sensor rotor. Unfortunately they claimed this is not covered by the factory warranty, so 3.5 hours and $200 lighter it was fixed. I asked the service adviser if this is a normal occurrence and if I could have cleaned it to resolve. He said, no this is not normal and no I could not have cleaned it as the speed sensor with the piece of metal attached is in a sealed hub. The hub was removed to access the speed sensor, which was then cleaned of the foreign material, and then reassembled."

Questions:
1. Has this happened before to anyone?
2. Any speculation on how the "thin piece of metal" got there?
2. Should this repair, in a "sealed" unit, have been handled as warranty work?

Here's a section of the 04 Prius Manual on the subject:
link to c1235.pdf