The flowers do look much more like an x Amarcrinum or maybe even just a Crinum hybrid than Amaryllis belladonna. To get a better ID, please post a picture of the foliage. A. belladonna does not have foliage when it flowers. Crinums generally have long, floppy leaves while x Amarcrinum leaves are shorter and more upright.
Do you remember if there was any foliage? Even if you don't remember exactly what the foliage looked like, its presence would exclude A. belladonna while its absence would exclude x Amarcrinum or Crinum. Just going by the flowers, it looks more like a Crinum hybrid to me. Neither A. belladonna nor x Amarcrinum have the long, curved "neck" at the base of the flowers, but Crinums do. Also, there is evidence of flowering over an extended period from the scapes (note faded flowers). A. belladonna flowers on a scape tend to open at about the same time.