For my views, I am presuming that concerned inward-supply is not at all recorded in books of accounts of the tax-paper. And it is not merely a case where concerned ITC is mistakenly expensed out (along-with basis value of inward-supply) in the books of accounts.
As per Section 16 (1), registered person can take credit of input tax chargedon any supply of goods or services or both to himwhich are used or intended to be used in the course or furtherance of his business.
If books of accounts of the business does not show these as 'supply' as received by the registered person and GST there-on as charged to him, question of availing ITC there-against - merely because it is reflecting in GSTR-2A - does not arise.
And in such a situation, another requirement to take ITC as per Section 16 (1) about 'such inward-supply being used used or intended to be used in the course or furtherance of his business' would not even arise.
These are ex facie views of mine and the same should not be construed as professional advice / suggestion.