As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REPORT STATES REAR DOOR DEPARTED ACFT APPROX 10 MINUTES INTO FLIGHT, ACFT JUST LEVELED AT 3500` FROM 2000`. INSTRUCTOR AND STUDENT BOTH STATE NO PREVIOUS ANNUNCIATION UNTIL SHORTLY BEFORE DOOR DEPARTED. DOOR NOT RECOVERED. FAA INVESTIGATING THIS OCCURRENCE. MANDATORY SB40-070 HAD NOT BEEN COMPLIED WITH AT TIME OF OCCURRENCE. ONLY MINOR COSMETIC DAMAGE REPORTED ON ACFT.