There is a chance that if the battery discharged completely 0% or so. And if the battery had some age to it, it could have been damaged. You could try several charge/discharge cycles to see if you can recover some charge time life.
Is that the model that the battery is glued in and not easily replaced?
Now that I have several devices, I try and make sure that the ones I am not using are turned off and not in standby/sleep, just for that reason in the o/p. And try and make a point to check every month and recharge as needed.
I have found with all of the rechargeable battery's in all my toys that to keep them from going bad because of non use (out of sight, out of mind)
That the best way to keep on top of everything is to set a repeating calender notification to check battery's every month.
Works great for my case of "c.r.s" and keeps things up and ready when needed!