Is the waiting period (iddah) obligatory for a wife who did not know of her husband's death until six months after his passing, and what is the evidence for that?

The iddah (waiting period) of a widow begins from the time of death. If she is pregnant, her iddah ends upon delivery. If she is a free woman and not pregnant, her iddah is four months and ten days. If she is an enslaved woman, her iddah is two months and five days. If she does not learn of the death until six months later, her iddah would have already ended before she became aware of it.