Complete removal of all disc material is impossible. It's true the surgeon will take out as much as possible, even scraping the endplates where the disc attaches to the bone.
A total discectomy is done to reduce the chances of another herniation. If any portion of the disc remains (even a small fragment or piece), problems can develop later. The disc fragment can move within the spinal canal or lodge against the spinal nerve causing nerve compression.
You may be having symptoms from disc re-herniation at the same level. You could be having problems with the disc above or below the previous level of herniation. The best way to find out what's going on is to see your doctor. An exam and imaging studies will help clear up the cause of the problem. A new treatment plan may be needed.