As investigators search for an estimated $1.2 billion missing from MF Global customer accounts, one customer says his entire account has vanished and blames the trustee liquidating the firm.

An Illinois-based futures fund on Friday said its more than $50 million account with the broker-dealer unit of MF Global Holdings Ltd is missing, and asked a federal bankruptcy judge to order the trustee to find it.

Highridge Futures Fund LLP said the trustee James Giddens has refused to help locate its account with MF Global Inc, even after transferring some 38,000 other accounts and giving customers access to some of their collateral.

Once run by former New Jersey Governor Jon Corzine, MF Global filed for bankruptcy on October 31 after a bet on European sovereign debt worried markets, causing a liquidity shortfall.

The Highridge fund said Giddens, CME Group Inc's Chicago Mercantile Exchange and regulators have told it nothing about the status of its account, which held commodity positions and cash. It also said it had been told twice that the account was being transferred, but the transfer never occurred.

This account is nowhere to be found, said the fund, overseen by Lombard, Illinois-based Highridge Trading Co.

The trustee's office has been in contact with Highridge, and will try to resolve the matter without the need for a court ruling, said Kent Jarrell, a spokesman for Giddens.

Giddens this week asked U.S. Bankruptcy Judge Martin Glenn, who oversees MF Global's bankruptcy, to allow the distribution of as much as $2.1 billion to former MF Global commodities customers, roughly doubling the total payout to $4.1 billion.

He said the payout should restore at least two-thirds of U.S.-based property to former customers of that unit, where funds were frozen because of the bankruptcy.

On Friday, the House Agriculture Committee in Congress voted to subpoena Corzine to testify about MF Global's collapse. A spokesman and a lawyer for Corzine each declined immediate comment.

Investigators believe MF Global may have diverted the missing customer money for its own needs. The amount missing is unclear, but a lawyer for Giddens has estimated the sum could be $1.2 billion or more.

The case is In re MF Global Inc, U.S. Bankruptcy Court, Southern District of New York, No. 11-2790.

(Reporting by Jonathan Stempel in New York; Additional reporting by Alexandra Alper and Charles Abbott in Washington, D.C.; Editing by Gary Hill)