Dear Customer (name blocked for privacy),
Although proving a verbal agreement is more difficult becauase there is no writing that can be easily shown to the court, that does not mean you cannot still file a suit for a judgment on the unpaid amount.
You can use the statements from your bank accounts, your written notebooks, any comments from friends of yours that know what happened, any copies of deposits made by your "friend," etc., to show proof that there was an amount of money given by you to this "friend" and that they did make some kind of payments to you. Because your loan amount of $30,000 was significant, you will not be able to file in small claims court - but you can file in other NY courts.
The NY courts have a system called "Court Help" that provides information, even forms, for people who are interested in filing their own claims, without the use of an attorney. You can obtain information about this from
http://www.courts.state.ny.us/courthelp/index.html__________________
PLEASE NOTE: Responses here are for information/education only, NOT legal advice and do not form attorney-client relationship! Only licensed attorneys you hire in your state can provide legal advice.