In Oscar a 1991 American slapstick crime comedy film directed by John Landis, I heard: "Your father just told me".
Why do not correct to say "Your father has just told me."?
Because in "How English Works" page 172, 16:
They (just discover) a new fuel - it's half the price of petrol and much cleaner.
The correct answer is by the book:
They have just discovered a new fuel - it's half the price of petrol and much cleaner.
Is there any connection with the fact that the book "How English Works" is by Oxford University Press UK, but the movie is by Hollywood in the USA?