The phrase "once recognized" is correct and usable in written English.
You can use it to refer to something that was identified, acknowledged, or accepted at a prior point in time. For example, "Once recognized as a leader, his influence spread throughout the city."
He argued that during embryonic development, immunocytes recognize 'self' elements and once recognized, the 'self-recognizers' are purged from the immune library.
A Rockets fan once recognized David from an interview he had done earlier in the day.
Wilsonian idealism, as Kissinger himself once recognized, is America's default foreign policy.
"Agon" was at once recognized as a beacon of radical modernity.
Lassalle at once recognized in the congress an opportunity to organize a "Suffrage Army".
Prime Minister Lloyd George at once recognized his abilities and made him minister of air.
Once recognized, though, how could that rupture not become a touchstone of much of what we think, say and do?
Contemporary audiences at once recognized the play as a masterpiece, but its form was subjected to an unprecedented critical attack.
A die-hard fan in a Chanel suit once recognized and harangued me in a bookstore about a story line involving an angel.
Mayor Michael Bloomberg, who now supports Mr. Silverstein's excessive demands for public funds, once recognized the hazards of overbuilding office space in the area.
I suspect that many, many writers have found themselves dealing with characters they have created who are waiting for something to happen, something "magic" (Naipaul) or something "momentous" (me) or something "prodigious" (James) that once recognized would change everything.
