I'm assuming it is wool, I can't imagine a synthetic rug smelling of anything much? We have an old Afghan carpet that used to belong to my mother and it has always smelt faintly (of goat?) but we've got used to it. We did try washing it once but it made it worse. Surprised that your more modern rug smells though, we have a carpet cleaning machine and even our wool carpets barely smell of anything once we've finished.
Do you have pets? I gather that it is hard to remove pet smells, and the water might have reactivated the odour. We use a concentrated Bissell Wash and Protect - perhaps this makes a difference? There is a version of this designed to remove animal smells. (Please don't be offended by the smelly pet suggestion, we have a cat and I can always smell him when we come home from time away!)