Would my saying to my wife, "I forgive you," after a phone argument in which I uttered a divorce out of ignorance of its rulings, and two years have passed since the incident, count as a رجعة (reconciliation) to her?

Your divorce occurred when you explicitly uttered the words of divorce, and your ignorance of its occurrence is not taken into consideration. Your saying to your wife, "I forgive you," is not explicit in revocation, and revocation is not achieved through it except with intention. If you had intercourse with your wife after the divorce and before the expiry of her iddah (waiting period), then she has returned to your marital bond.