Recover
When an exhausted skill die is removed from the cooldown trackCooldown TrackDice are placed here as the adventurer exhausts their skill dice or gains fatigue and status effect dice. The Cooldown stat determines the number of dice that are removed from the track each turn. by your Recovery step or another effect, you recover that die. Place it in the correct slot in your attribute rows. That die is immediately available to use. When a status effect die is removed from the cooldown track, return it to the supply.
A drainedDrainedThe ability is resolved instantly as described in its entry. Then, that die is placed on the adventurer's race sheet. It is unavailable for the remainder of the battle and is considered drained. die can only be recovered by an effect that specifically recovers drained dice, by visiting an inn during a townTownThese encounters are described in the gazetteer and are triggered when the party ends its overland movement in a town or rolls a 
result on the unstable die while at an unstable landmark (see Traveling Caravans). encounter, or during the End of BattleEnd of BattleA battle ends after the current round when any of the following occur: The party achieves the encounter's objectives, or the party retreats from battle, or all adventurers are defeated. Cleanup.
Remove vs. Recover Overfatigue Dice from Cooldown
When game text tells you to recover an overfatigue die in your cooldown track, treat it like normal for recovering overfatigue - it goes to the end of your cooldown track. When game text tells you to remove an overfatigue die from cooldown, you can remove it entirely.
If game text says to remove a fatigue die, you can choose between light or overfatigue.
There are a few spots in the rulebook where remove is used when recover would be more appropriate, but it should be generally understood that an overfatigue die that would leave your cooldown track is placed back at the end of your cooldown track, unless it's being removed by a game effect that specifically tells you that you can remove it.
Source