Difference forgot/did forget

I’m sorry if it is silly question.

While I was chatting with English native speaker, he said “I did forget it” while I was expecting he will say “I forgot it”.

The question is :
What is the difference between “I forgot it” and “I did forget it”?

Thanks in advance

‘did forget it’ is more emphatic.

You mean both of them are correct, but “I DID FORGET IT” is more emphatic ?