Does a divorce by innuendo, coupled with intention, take effect if the one uttering it is unaware that it constitutes a divorce, and believes that divorce occurs only through explicit wording?

If by the كناية (allusive statement) you intended the meaning of divorce but did not intend to effectuate it, then divorce does not occur. This is because the condition for its occurrence by كناية is the intention to effectuate it, not merely intending the meaning of divorce.

Ibn Hajar al-Haytami said: "And if he said 'I am from you... ba'in (separate),' or similar allusive statements, the intention of the divorce's origin and its effectuation is stipulated, like all other allusive statements."

Al-Dimyati said: "The كناية... requires the intention to effectuate divorce thereby."

As long as you did not intend to effectuate divorce by the كناية, no divorce has occurred by it.