As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
F/A FOUND UNIDENTIFIED WHITE RECTANGULAR PIECE OF PLASTIC AT BACK OF AIRCRAFT. ROUGE PIECE BROUGHT UP TO FLIGHT DECK FOR FUTURE IDENTIFICATION. GROUNDED - YES. REINSTALLED LIGHT COVER FOR AFT CABIN AISLE EMERGENCY LIGHTS, OPS CHECKS GOOD COVER SECURE.