Can a man take back his wife after the first divorce without witnesses, especially if the divorce was conditional and the spouses forgot that it occurred?

A man has the right to take back his wife after the first divorce as long as she is within her waiting period ('iddah), and having witnesses is recommended but not a condition. Conditional divorce takes effect when the condition it is tied to occurs, according to the majority of scholars. However, Sheikh al-Islam Ibn Taymiyyah holds that it does not take effect if the husband did not intend to bring about the divorce, and he must pay an expiation for breaking an oath (kaffarat yamin). If a divorce occurs, and the spouses engage in marital intimacy during the 'iddah of a revocable divorce, some scholars are of the view that the return (raj'ah) occurs by this action, even if there was no intention of taking her back. As for what was forgotten, if the action on which the divorce was conditioned was done out of forgetfulness, then the divorce does not occur.