If any cell dropped below 3v, you should dispose of it.
It could be your charger also. If you are using the stock charger, I am not sure at what cell voltage it considers a damaged battery. If all cells are over 3v though, you should be able to bring it back. May need a "real" charger to do that. If you want the battery to last, do not dischagre below 3.5v/cell. With the H, that would be 14v total which you probably would have been warned, or auto landed.
I am landing at about 14.5v now since I have flown my batteries enough now and see they are holding up by checking internal resistance and cell voltage checks.
Here is some good info for you A Guide to Understanding LiPo Batteries
I've seen a way to "revive" a lipo that has been run too low. So low the charger won't recognize it. After using this alternate method the Lipo appeared to work normally. I personally wouldn't chance it with my birds. But this "revival" was for R/C cars and it seems to work...
I won't share this method as it involves charging the lipo in a non-standard way that could start a fire...
Mine hit stuck on the flashing blue lights on my stock charger.
I then modified the stock charger to work on an external LiPo charger.
When testing the battery prior to charging the external LiPo charger only found 3s. But my program was for 4s. I hit start anyway.
After 30 seconds, I stopped it and returned to the original factory charge setup and it started fine again.
So short answer is keep it and do the charger modification or get a charging lead.