Simply go back to the question slide and left click on the graph icon (Fig. 4)
to redisplay the data/graph.
Fig. 4 - Graph Icon
Warning: if you right-click the icon, you will delete the data from the previous poll and ready the icon for new polling data (Fig. 3), it does overwrite the data, so please make sure you have saved the presentation under a different name if you want to retain the original data.
Fig. 3 - Poll Icon