The doctors at the CEC do not perform diagnostic-only laparoscopies. All surgeries are done with excision of endometriosis as the goal. My GYN said no endo was seen but I had pelvic adhesions, which he removed. I still have pelvic pain, bloating, menstrual diarrhea, irregular periods. Yes, it is possible for endo to be missed at surgery.
Endometriosis can have many appearances, from very obvious to extremely subtle.
If a surgeon is not thoroughly familiar with all the manifestations of endo, it is possible that some will be missed. Endo can often hide underneath adhesions. The fact that you had adhesions at all is suspicious, unless an obvious reason for them was found. Also, endo can hide. At surgery, every corner of the pelvis needs to be checked.