CREATE TABLE table_74551 ("Date" TEXT, "Opponent" TEXT, "Venue" TEXT, "Result" TEXT, "Attendance" TEXT)

Which opponent has unknown attendance, and lost 2-0?
SELECT "Opponent" FROM table_74551 WHERE "Attendance" = 'unknown' AND "Result" = 'lost 2-0'
SELECT "Opponent" FROM "table_74551" WHERE "Attendance" = 'unknown' AND "Result" = 'lost 2-0'