How to audit credstash activity in cloudtrail logs?

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README briefly says that credstash activity is logged in cloudtrail logs:

These encryption context key value pairs are useful to provide auditing context to the encryption and decryption operations in your CloudTrail logs. They are also useful for constraining access to a given credstash stored credential by using KMS Key Policy conditions and KMS Grant conditions.

I've tried to lookup in our cloudtrail logs and find nothing except of my own activity (and I'm admin of the account). Can you you elaborate a bit more how credstash activity goes into cloudtrail?

PS I will provide PR to update README as soon as someone helps me with understanding how it works