Both forms are correct. The simple past shows a one-time event that is complete: I am late for his party because I forgot where I put my keys. The perfect present shows that there is a time period during which the forgetting happened.
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JesusenglandI can't understand whyIt's often a puzzle to non-native speakers, and yet there are many examples of it. Certain events are regarded as occurring at a definite point in time (even though that point in time is not made explicit in words); theyis usedthe Past Simple is used ...