The State Department entrusted millions of dollars in travelers checks to poorly paid clerks who kept them in unlocked cabinets and in stacks on the floor, resulting in an operation so loose that $59,000 was embezzled and $307,780 has disappeared, Congress was told. Congressional investigators also told a House Government Operations subcommittee that controls on State Department travel advances were so disorganized that $15 million in such payments are delinquent. That total includes a $695 advance to fired White House aide Lt. Col. Oliver L. North, which is four years overdue. Some of the names on the travel-expense accounts appear to have been replaced with fictitious names, the investigators said. One delinquent traveler is recorded as "Ludwig Van Beethoven."