By Matthew Goldstein

With the mystery of the missing $600 million in customer funds at MF Global Financial still unresolved, a lot of customers of the failed futures firm are starting to complain about getting bounced checks.

It appears that 10 days ago, with speculation swirling that the Jon Corzine-led firm would soon file for bankruptcy, a good number of customers started to put in requests to pull their money from the New York-based outfit. But instead of simply wiring that money back to their customers, it seems MF Global tried to buy some time for itself by sending that money back via snail mail in the form of an old-fashioned check.

Those checks cut by the folks at MF Global began arriving in customer mailboxes this week, several days after the firm filed for bankruptcy on Oct. 31 in New York federal court. And by the time customers started depositing those checks, they were rejected as having insufficient funds.

It’s not surprising the MF Global checks were rejected after the bankruptcy filing. It’s pretty customary for all expenses to require court approval once a bankruptcy judge gets involved.

But the move by MF Global to send back customer money by check has left a lot of customers in a bad predicament. I’ve been talking to one futures trader who says he and some of his associates have well over $1 million in bad checks issued by MF Global. Those checks were issued on Oct. 28–three days before the bankruptcy filing. The trader is considering producing a copy of the check as evidence of what he sees as MF Global’s bad faith in dealing with it customers and Wall Street’s broken system for dealing with customer money.

Says my source: “I am totally disgusted with the way the industry has not responded.”

It’s not clear how many MF Global customers got checks that have bounced. But online message boards are filling up with complaints about the situation.

In the end, the issue of bad checks may pale in comparison to the missing $600 million in funds. But it is indicative of just how disorganized things were at MF Global in its waning days as Corzine & Co. raced to find a buyer for the firm.

But there was no savior for MF Global. A potential deal with Interactive Brokers fell apart at the last minute when the issue of the hundreds of millions of dollars in missing money became apparent.

In the wake of Lehman Brothers collapse, its worthless stock certificates and debt notes became something of a collector’s item. Maybe the same will happen for MF Global’s bounced checks.

UPDATE: I highly recommend this story by my colleague Lauren LaCapra on some farmers who have been impacted by MF Global’s fail.