`_id` is a special field: https://www.elastic.co/guide/en/elasticsearch/reference/6.2/mapping-id-field.html

You can't search in it like any normal field. Just few queries are supported.

If your use case requires to wildcard search on it (bad idea BTW), then you need to use one of the supported queries:

> The value of the _id field is accessible in certain queries (term, terms, match, query_string, simple_query_string).

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