South African Central Bank Governor Gerhard de Kock abruptly left Washington yesterday after canceling a press conference scheduled for today in which he had been expected to discuss the results of a whirlwind trip triggered by South Africa's debt crisis.

Only the elusive South African banker knows why his Labor Day trip to Washington was cut short.

At least no one else admits to knowing what kind of reception de Kock received during his two-day visit or why he left unexpectedly.

Even the South African Embassy spokesman swore he had no knowledge of de Kock's schedule.

De Kock arrived here Saturday after discussions with banking officials in New York and London during the week about his country's $12 billion in short-term loans that fall due during the next 12 months.

Citicorp met with de Kock but refused to comment on the talks. Chase Manhattan Bank said it had not met with the South African. It was not clear yesterday if de Kock's mission had been to try to reschedule the debt or to warn the banks of a package of financial measures announced by the South African government over the weekend.

His sudden departure followed South Africa's unilateral suspension of foreign debt repayments and imposition of foreign exchange controls Sunday.

Embassy spokesman Peter Swanepoel gave no reason for canceling the press conference and said he had no information about de Kock's schedule here or his next destination. But the switch in plans was seen by some as an indication that de Kock had made little progress in securing fresh credit from American banks that have started calling in loans.

Financial analysts have assumed widely that de Kock came here to meet with Federal Reserve Board, International Monetary Fund or State Department officials.

Fed officials reached at home either protested that they were still on vacation and knew nothing or refused to comment. The International Monetary Fund refused to confirm or deny that it had any contact with the bank official.

A Reagan administration official said Sunday that the administration was reluctant to become involved in Pretoria's financial crisis, noting: "We want to stay out of this as much as we can."