You should be searching based on the host value you specified for the input data. The above metrics.log event only confirms that data has been sent, and there is only a very small amount (5k). Typically, you can search for your data based on the host, source, or sourcetype. So utilizing a wildcarded search with the source name (timerange over all-time) might be a way to find your data. Another possibility is that your events are so small that Splunk has not filled the buffer queue. In that case, you should try sending a complete log file.
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