Being in the hospital "for another condition" could provide some cover.
Not everyone who has a sex change operation feels the need to rub their new plumbing in all the world's faces.
I think it would be very rare for anyone over middle age to have gender issues. ID theft on the other hand, is common.
However, if you are thinking that she is still alive, masquerading as a man - there would have been no need for surgery. Hormone treatment would do it...
But for what purpose?