You have to accept that its a cost of doing business. Whoever you deal with in business you are always going to get some scammers. The number should be pretty low though and you can build the cost into your pricing. If the number of times you get scammed is high then something must be going wrong somewhere.
Of course, you should still dispute it with fiverr, but don't waste too much time mulling it over, otherwise it will bring you down.