Almost every Special Unlock item may be reclaimed if it has been accidentally discarded. Simply return to the Legacy Unlocks tab in the C-Store and claim your item again.
If you have trouble reclaiming a Special Unlock please verify that it is not equipped on your character or stored in the inventory/bank.
Remember that some special unlocks have faction restrictions (tribbles/targs) while others are limited to being claimed one time only (bonus skill points/costume pieces).