You can use the below AQL query to search for the artifacts having the sha256 value.
curl –u username -X POST "https://test.jfrog.com/artifactory/api/search/aql" -H "Content-Type: text/plain" -d 'items.find({"type":"file", "sha256":"6120be6a2b7rtvv3665d0cbddc3ce6eae60fe94637c6a66985312d1f02f63cc0bcd"})'
Also make sure to verify and delete the sha layer from the Trash can as well. After deleting the layer, perform a Zap Cache on the repository and then you can try pulling the Docker image again from the repository.