I'd second it being saunf purely on the basis that, despite racking my brains, nothing else seems to fit. But while saunf certainly would add some sweetness, the amount needed to be added to actually affect the sweetness noticeably would impart quite an aniseedy flavour to the dish. Not a flavour I associate with dhansaks of old but maybe the new style has incorporated it ... or maybe it's just a regional thing. Or I suppose it could be dried ginger which is sont or saunth, which sounds closer to "sote" but I wouldn't expect any sweetening effect from it.
I'd be willing to bet though that, as you mention, 99% of dhansaks are made with jaggery and/or white sugar so maybe it was just a misunderstanding.