Suffolk County National Bank Cleared fraudulent cashier check & stated funds are good with in 24 hours Amityville New York

Sorry to tell you but in the end you are the one who is to blame.

Now, as an observation, the very first thing you pointed out was that this was from a "legit" business.  So if this business is so legitimate, why is there not one sentence about you going back to the business to make sure they "make it good"?  I'll tell you why...because you in fact got scammed.  It was either a company offering you a "Secret Shopper" job paying a few hundred dollars(when legitimate secret shoppers get $5-$10 per job), or offering to buy something you had advertised on a internet site for sale.  Where in both cases they came up with an excuse/reason to have you cash it, and send a good portion of the check via western union to one of their "partners".   This scam works because they deal with your "greed" where you let your commons sense go away for a few extra dollars.

You say why couldn't the bank protect you?  Because the bank is under very specific regulations.  One such regulation is the Federal Expedited Funds Availability Act.  This specifies the maximum amount of time a bank can "hold" a deposit. Cashiers Checks are basically consider cash, and as such they are required to release the funds within 1 business day.  Had the bank held your funds longer they could actually get in some legal trouble.  But it may take 2-7 days for the bank the check was written on to verify the check, yes even in 2016.  Scammers know this and use this to their advantage.  

You ask why you are being held responsible.  When you deposit a check, you are making the assertion that it is legitimate.  After all if you were depositing a check that you knew was fraudulent you would be committing a crime. This makes the bank a "Holder in Due Course".  Meaning that the bank is just an intermediary and if it does come back as bad, the depositor(you) are held responsible.  This now goes back to my first assertion, as just as the bank is holding you responsible, you would have to hold the person/business who gave you the check responsible.  But if this is a scam...there is no one to go back to and you are legally responsible. 

FYI the police were wrong, this is not Identity Theft...At least not where someone took your identity.  Now, the name of the company you got the check from is a victim of Identity Theft and they won't be held responsible.  But you are still responsible.  Now, it can get worse for you.  While I am not saying this will happen or even has a high chance of happening. But there is a possibility that if you fail to pay back the money the bank could file criminal fraud charges on you.  Because you should have been aware that this was "too good to be true" and a scam.

In the end let me just give you some advice.  ANYTIME someone you personally do not know sends you a check and asks you to send a portion of the amount back..it is a scam.  It doesn't matter what reason they give you, it doesn't matter how good they make it sound, it doesn't matter what they say...just remember it is a scam and the best thing to do is just shred and throw away the check.

Sorry and good luck.