A:
This is an interesting question that might cause a debate among parliamentarians.
Although arguable, it is my opinion the election should stand.
Here is my reasoning.
A member may be elected to office regardless of whether he has been nominated.
(See RONR p. 431.)
Although the absent member's name shouldn't have been placed in nomination from the floor, that should not invalidate his election.
No one's rights were violated, and it's likely your organization elected the officer it prefered.
In any case, because a majority is required to elect, the runner-up cannot fill the office should it later be declared vacant.