Finding nested ATO models

Summary: I have nested ATO models, i.e. model A contains Model B which contains Model C. Need to find what upper level configured instances of Model A and B are using a particular configured item for Model C.

Content (required): If a sales person incorrectly configures an instance of Model C, I need to disable matching for it. However, if it has been used in an upper level ATO model how do I find which specific models are using it. The Oracle docs say "Use the configured item REST API" but don't give any actual guidance how to use the API...