How can one avoid the suffering after getting cheated? Today I suffered severe disappointment because I thought I was cheated some amount of money. I couldn't complain to anyone because I had no proof. And I suspect those who cheated me will also cheat other people.
I want to avoid such disappointments in future and also I want to do the right thing. 

What should be my response on getting cheated ? Should I forgive the thugs who stole my money ? Should I wish bad for them and report it to the police or the managers?
First, do not hold ill intentions. It may or may not be a case of cheating, there could be misconceptions.

Secondly, if you really got your money cheated, just report to the police or managers. Do it out of due diligent intentions, nothing more nothing less.