Rti related query

Information exempted under section 8 and 11 can be denied under RTI. According to Section 8 (1) j, Information can be denied if it is related to personal information, According to section 11 Information can be denied if it is related to the third party. Sir now my question is - Information sought by the applicant can be denied using both the above sections only if such information is available in the record. But if the information sought is not available in the records, then how can such information be related to the personal information and the third party information? In such a situation how can the above sections be used by PIO to reply the RTI? Is it not better for the PIO that he should answer that the information sought is not available