Can we sue for medical malpractice (long details inside)

My mother has had issues with her abdominal wall since having a hysterectomy years ago. She had another surgery to repair some hernias afterward, but I guess the surgery wasn’t very successful and basically her abdomen was all ripped up on the inside. Causing her years of pain. This past Friday I went with her to have yet another surgery to repair the abdomen. I watched her sign a consent form to repair the left side using that mesh stuff. While in the operating room she asked the surgeon to take a look at the right side as well because she’s been having intermittent pain, and he agreed. I went to visit her after the surgery and found out the surgeon operated on her right side. Only. And didn’t even use the mesh. The doctor came in for a post-op visit and when I asked why the left side wasn’t done he gave me a funny look and said he was supposed to focus on the right side. When my mom challenged this he said “we’ll see”, mumbled a few things to his intern and left! So basically he didn’t do anything he was supposed to. My mom went for several pre-op visits so I’m not sure why he’d forget what he was operating on. Obviously my mom is very upset and I’m trying to get a hold of this doctor but his office is saying she doesn’t come in for 3 weeks for her post-op appointment. My mom is going to have to have another surgery to finally fix this problem and now she is in even more pain as she has to recover from this unnecessary surgery. She cannot work, she won’t collect disability because she thinks she’s cheating the government, and though I don’t mind, I have to stay home to take care of her. I don’t know what can be done here, but I am so upset and wondering if this could be medical malpractice or negligence? Do you think a lawyer would take this case or is it a lost cause? We live in Canada.