As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) A PASSENGER REPORTED THAT THEY SAW A PANEL FALL OFF THE ACFT ON TAKEOFF. IT WAS CONFIRMED THAT THE LT HYD SERVICE PANEL DOOR WAS MISSING. THE ACFT RETURNED TO THE DEPARTURE AIRPORT WITH NO ISSUES. IT IS SUSPECTED THAT THE DOOR WAS LEFT UNLATCHED AFTER MX AND WAS TORN AWAY BY THE AIRFLOW ON TAKEOFF. A TEMPORARY BLANKING PLATE HAS BEEN INSTALLED IAW RD 8/4-54-039 TO ALLOW CONTINUED OPERATION OF THE ACFT. DOOR, PN 85414708-103 (IPC 54-21-11, FIG 1-15A).