What was found
(CAN) WHILE FLYING WITH ALL DOORS OFF, THE COMMUNICATION PANEL (THE PANEL THAT OPENS THE CABIN TO THE REAR CARGO HOLD) FLEW OUT OF THE CABIN. NO DAMAGE WAS FOUND ON THE REST OF THE ACFT. THE PANEL HAD RECENTLY BEEN MODIFIED FOR A STRETCHER KIT INSTALLATION IAW SB 25-016. THE PANEL WAS INSTALLED CORRECTLY WITH ALL THE FASTENERS AT THE TIME OF THE INCIDENT. THE CREW WAS NOT ABLE TO LOCATE AND RECOVER THE PANEL.