Yeah, there are cis women born without labia minora, but it's not *typical.* So I'm rather startled that they routinely do not even try to create inner labia.
What is used varies by surgeon, but in general, unused tissue is discarded... suggesting that, indeed, what might have been used in your case will no longer be available post-op.
However, there is always the option of a skin graft; the downside is that the skin will be taken from elsewhere, creating a new wound and likely leaving a scar, but the upside is that this is a possibility that is essentially permanent as a method of correction.
(Brassard creates the outer side of the outer labia from the hair-bearing skin of the scrotum [which reflects the fact that cis women grow hair there], the inner side of the outer labia and the outer side of the inner labia from hair-scraped scrotal tissue and/or a perineal graft [the skin removed at the site where the vagina will go is saved and used as a graft], and the inner side of the inner labia from urethral mucosa that was removed from the penis when the urethra was shortened. All of this skin would in fact be either used or discarded; there's no real way to "save" any of it with a blood supply post-op.)
