Aircraft Maintenance Technician reported wing access panels departed the aircraft inflight due to possible missing or damaged part.

Narrative

On the weekend of Day 0 - Day 3 I was performing several maintenance tasks on Aircraft X; one of those being lubrication of slat; ball drive screw nut; and slat roller assy. I was alone performing this task for both wings. I opened each panel; performed lube task; then closed access. Ref A300 AMM XX-XX-XX. The aircraft departed Day 3 night from ZZZ1-ZZZ. Upon landing and walk-around inspection performed by pilot [they informed us] that two inboard leading edge panels were missing. Field service was sent up to ZZZ and verified all hardware was installed on the aircraft from where the panel left. When the panel left the aircraft it tucks underneath the panel outboard of it and it made that one depart the aircraft as well. To my understanding; I performed the task at hand correctly and closed access correctly. There is a bracket on the aircraft that is either missing; or damaged that caused the blow out panel to leave the aircraft; and other aircraft I believe have been reported to have that damaged; or missing as well.