You can also see that the data is actually in the partitions by using the system views. Of course you would have to look at some of those numbers there...
As partitions are a concept of data structure management "below" the SQL layer, the only way to address single partitions is to provide a fitting WHERE clause.
For example you can unload your table and select only the data you want and check what partition had been touched for this.
On top of this you might even have a look into the partitioning trace output to confirm that the right partitions are mapped to your request.