You can only search "analyzed" fields with a wildcard. To view which fields are analyzed within your account, go to Kibana --> Management --> Index Patterns. You can sort the list by the Analyzed column to make it easier to see which fields are analyzed. By default, we do not set all fields to be analyzed because it can slow down the performance of your account and take more space within your index.
If you want to have a field set to analyze, you can contact support via chat and we will be happy to make the change.