It depends on where you are located. We (out of the Appleton, WI) airport have never had Allegiant flights for the months of mid Aug-mid Nov. We also are missing a few "non-demand" dates for May. If your airport is not heavily traveled during that time, they may discontinue service for a while.
If you change your departure destination and see that others are getting rates and your airport is not, this is probably occuring.
This was the first year they removed May from our flight schedule. I called to see what happend and they explained the above. You can call, but it took forever to get through.
Hope this helps...then again, I hope you do see your flights and they did not "black you out" for a bit.