The implementation is free to decide whether deposits can be recovered directly, or if they will be locked in the smart contract - temporarily or permanently.
For the duration deposits are locked, they are part of the smart contract's swap liquidity. During this time, locked deposits may only be withdrawn in exchange for other tokens accepted by the contract.
Deposits that are not locked should be withdrawable using the @code{withdraw(address,uint256)} (@code{0xf3fef3a3}) method signature.
Of course, as with most swap contracts, the tokens available for withdrawal by the holder may not necessarily match the tokens that were deposited by the holder.