A: Did you find the Book?
B: No. I searched a lot but could not find it.
A: Do you remember we sent a gift to the Manager?
B: No. I don't remember.
A: Did you call the Travels?
B: Yes. But I couldn't get through. (or His mobile was switched off)
A: Did you remember that we sent a fax to the customer?
B: No. I did not remember.
or No. I do not remember.
The past tense could be used if you are asking afterwards, but the present tense sounds more natural without more context.