I had bought one some time ago, in case a day happens that I am unable to reach the daily XP. Well yesterday was a day like that, but I guess this feature's title is misleading. My streak reset, and that option proved worthless.
Have you been checking regularly to see it wasn't used before this? I've had mine used a few times that I hadn't been aware of, and needed to repurchase it to keep it current.
It's good practice to look every few days to see if you still have one in place.