Three months ago, a weary San Francisco hotel night clerk allegedly gave a equally weary Washington traveler a "hard time" when he tried to charge his bill.

The clerk, who may or may not still be with the Hyatt Corporation, told Robert E. Barnett that he could not bill his "company" for a 2 1/2-day stay. This despite the fact that Barnett's office had made the reservation well in advance and did - up until that moment - a lot of business with the Hyatt people.

Barnett is chairman of the Federal Deposit Insurance Corporation. FDIC is a quasi-government corporation with an $8.5 billion credit rating and 2,400 employees who are constantly traveling and staying in hotels and motor inns.

Since that fateful Sunday evening in March the FDIC has soured on Hyatt facilities. It has advised examiners and other employees not to stay in any Hyatt hotel or use its facilities on official business unless nothing else is available.

Edward Phelps Jr., the FDIC controller who issued the negative travelers advisory, said that chairman Barnett didn't make a fuss over the San Fraancisco incident. He just mentioned, Phelps said, that he tried to get the hotel to bill FDIC for the trip, which was official. When the clerk refused, Barnett had to pay the tab with the only personal check he had with him.

Six days after the episode, Phelps sent FDIC offices around the country a memo. It said: "As a matter of corporation policy and to the extent possible in connection with corporation business, please avoid the use of Hyatt hotels rooms, and Hyat conferences and other facilities henceforth." An FDIC official said he didn't know how much business his agency did with Hyatt, but "whatever it was, it is down 100 per cent now."

Phelps said he ordered the boycott not because the chairman was involved in the incident, but because he didn't want other FDIC employees to have the same problem. "I'd have reacted the same way if it had been an examiner," Phelps said.

Phelps said that a "regional manager" for the Hyatt coporation had visited him earlier this week and had apologized for the incident. Phelps said that as a result of the talk, he expected FDIC would "reconsider" its anti-Hyatt order in the near future.

Fred Alexander, regional vice president for Hyatt's northeast operations, confirmed that he did visit FDIC Tuesday and saw Phelps. "I did pay a visit out of courtesy, I thought we owed him that. I explained that it had been a misunderstanding and I think we have the situation straightened out now," Alexander said.

For its size, the FDIC is one of the most-traveled federal agencies. More than 2,400 of its 3,500 workers are bank supervisors or examiners who are constantly visiting banks and institutions insured by the FDIC.

Barnett, a long-time FDIC official, has also been a busy traveler since taking over as chairman.

In addition to the March meeting in San Francisco with a western bankers group, Barnett was in Manila in January to speak to the Philippine Deposit Insurance Corporation. Last November he went to the Tan-Tar-A Golf and Tennis Resort in Osage Beach to address the Missouri Bankers Association. The month before that he was in the Connecticut Saving Banks Association meeting at Dorado Beach, Puerto Rico, and in December he was again in Puerto Rico, at the San Juan session of the Puerto Rico Bankers Association.