In order to get the money from the third party, the third party must somehow be liable to you. You had a contract for payment with Gehl. Where there is a contract at play, the only time that a third party will be liable for payment is when the contract specifically states that they will pay (i.e., they are a guarantor), or they are a third party beneficiary
Based on the facts you have stated, there is no legal theory that allows you to get the money back from the third party. The other party does not owe you the money and has no reason to return it. It is Gehl who gave the money to a third party, presumably in return for goods.
To sue Gehl, you would be best suited to file the suit in the county where they are headquartered. Because the amount is $12,000.00 that you are after, you will need to file suit in district court
. It is too large of a claim to file in small claims
Because the claim is handled in district court, the rules of evidence and rules of civil procedure
will apply, so you will need to hire a lawyer to handle the claim.