Would the statement made in anger by someone, in response to being reminded that honey contains healing for people, "Does this mean we read the Quran and don't buy medicine?!" be considered a denial of Allah's verses in the Quran and regarding honey, or an act of disbelief and apostasy from the religion, necessitating a ritual bath and renewal of the Shahada?

Disbelief is not incurred by stating that honey contains a cure for all diseases, because it cures many of them, though not all. Ibn al-Qayyim mentioned that it is not a treatment for those with a yellow bile imbalance. As for the Qur'an, it is entirely blessed and a healing. Ibn Baz says: "The entire Qur'an is a healing from beginning to end. If one recites Al-Fatiha, it is the greatest surah in the Qur'an, repeat it... And the entire Qur'an is a healing if one recites from it whatever Allah facilitates..." There is no harm in using other medicines, just as the Prophet, peace and blessings be upon him, and the early Muslims would treat themselves with natural remedies.