Disappearing dermoid/endo?

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I had an endometrial cyst removed twelve years ago and heavy , painful periods since. For a few years I just lived with it, then in recent years returned to the gp and had a scan where I was told I had some calcification on my left ovary but that this was just the ageing process and no action was needed. My periods got worse so I was was prescribed mefenemic and tranexamic acid by another gp. Earlier this year a scan showed a probable dermoid cyst (seemed to have solid and liquid parts) on left ovary, uterine polyp and adenomyosis. I had a hysteroscopy to remove the polyp (only Improved periods for two months then back as bad as ever). A few months later I had another scan which confirmed the dermoid was still there on the ovary and had grown a bit. Was told as it was going nowhere and its appearance had changed I would need it removing, and was also advised to have the ovary removed. Had laparoscopy for this on Monday and was told when I came round that they found no cyst on the ovary (so the ovary had not been removed) but they removed Endometriosis patches. i am not sure whether this had been on the ovary or somewhere else and I was really groggy so didn't ask. I haven't had my follow up yet. I am happy to have not lost the ovary as I was worried about the hormonal impact, but I am just confused now as I can't understand it, how two separate scans could see a cyst with solid parts then it not be there when they look inside. I know liquid filled cysts can resolve themselves but didn't think partially solid cysts could? Could it be inside the ovary instead and been missed? also can this Endo come back? Am very confused. Has anyone else had a similar experience?