A state file containing reports of physical and sexual abuse of foster children, based on interviews with some of the children and including one instance reminiscent of slave auctions, has been turned over to the Executive Board of the Nebraska Legislature. One of the reports in the file ... is an account by [a] victim who described parties at various places, including Omaha and cities to which she was flown on the East Coast ... including one in which the ... teen-ager was made to stand nude at a party while she was offered at auction to the highest bidder. I don't know if they can prove it," the source said, "but if one-tenth of what that girl is saying is true, I'd sure hate to have her talking about me." The foster care agency's submission of the file is among the latest developments in a case that began surfacing Nov. 4, when the Government's National Credit Union Administration shut down the Franklin Community Federal Credit Union in Omaha. The agency ... subsequently filed suit against Lawrence E. King Jr., Franklin Community's manager and treasurer, charging him with diverting millions of dollars of the institution's money to his own purposes. In all, the agency says, Franklin Community is missing $38 million. Mr. King has not been accused of personally engaging in child sexual abuse. But a number of widening Federal and state investigations into the credit union's collapse are aimed in part at determining whether any of the money he is accused of embezzling was ever used to transport children or to pay them for sex.