I’ve reviewed Release notes and found out that Singlestat and Gauge were split in 6.4.0 - see release notes. So since 6.4.0, gauges are implemented in the separate gauge panel, not the singlestat panel. We are also not going to support sparkline in the gauge panel in the future as it makes very little sense to mix them and it doesn’t look good.
To solve your issue - since 6.4.0 (see Dashboard : Reuse query results between panels in 6.4.0 release notes), you can now share data between panels. This will let you put a gauge next to a small graph using the same query results. Just create new panel, choose Dashboard as a datasource and choose the panel from which you want to use the query. This query will be reused in your new panel.