Mixers have minimum amount of coins that they can mix. If you do not send up to that minimum amount for mixing, it would be considered as donation.
The minimum deposit can be 0.002 BTC.
Can you let us know the amount of the coin that you sent for mixing, and the name of the mixer?
He even contacted them regarding his issue and he was told his deposit was not up to the minimum required amount.
Not exactly. They didn't contact me back. It was a message that appeared after paying saying see ya sucka.
Obviously not in that verbiage but might as well have been.