It’s a color scheme and not a full theme, it’s selected in the wizard step at /wizard/steps/colors. The theme should be created again when the wizard is re-run, but it would also set it to the site default.
You can recreate it manually using these colors:
"primary": "d9d9d9",
"secondary": "3d4147",
"tertiary": "fdd459",
"quaternary": "fdd459",
"header_background": "36393e",
"header_primary": "d9d9d9",
"highlight": "fdd459",
"danger": "e45735",
"success": "fdd459",
"love": "fdd459"