Chemistry teachers sometimes lie to keep things simple, and sometimes they are plain wrong about the details. They are people after all.
For example, there is a reaction in which ozone changes to oxygen gas. It's catalyzed by hydroxyl radical and the mechanism is believed to be
OH + O3 --> HO2 + O2
HO2 + O3 --> OH + 2O2
Notice there is no OH in the intermediate step. It doesn't exist any more because it's reacted and become something else. However, by the end of the reaction, it's back again - it's been regenerated.
Note that it's not a good idea to point out to the teacher things like this. Sometimes they get annoyed. Sometimes they'll argue with you, and in an argument like that, you lose even if you're right and the teacher is wrong. Just accept what they tell you and spit it back out on the test.
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