Advaita DIpikA, vol. 2, p. 145-147 states - अस्मत्-अभिमत-अज्ञानं तु सुषुप्तौ अपि विषय-व्यावृत्तम्-एव अनुभूयते। विषयस्य अपि अज्ञाततया नित्य-अनुभव-मात्र-वेद्यत्वात्। न चैवं जागरण इव ‘अहमज्ञो घटं न जानामि’ इति प्रत्ययप्रसङ्ग इति वाच्यम्। तदा अज्ञान-साक्षिणः सविकल्पकता-आपादक-अहंकारस्य-अभावेन तथा-अननुभवात्।
किञ्च सुषुप्तौ ज्ञानादि-अभावो अपि साक्षिणा अनुभवितुं शक्यते। न च एवं तदा अज्ञानादि-असिद्धि प्रसङ्गः। तस्य तदा अपि आवश्यकत्वेन जाग्रति इव ‘न अवेदिषम्’ इति अनुभवस्य तदेकविषयत्वात्।
The crux of the issue is as under. No matter what the vishaya is, it is always sAkshi-bhAsya. However, only-vishaya or only-ajnAna is never sAkshi-bhAsya. jnAtatva-vishishTa-vastu or ajnAtatva-vishishTa-vastu is sAkshi-bhAsya. Now, sushupti is sarva-vishaya-vyAvritta-ajnAna-anubhUti as we recollect - I did not know anything. Means, the ajnAna experienced in sushupti was vishaya-vyAvritta. However, since the objects were ajnAtatayA-sAkshi-vedya and there was no ahamkAra, there is no experience in sushupti in the form of “I don’t know a pot”. Similarly, jnAna-abhAva as a visheshaNa of ajnAna is experienced by sAkshI ajnAtatayA in sushupti.
In jAgrat, the past jnAna-abhAva i.e. jnAna-abhAva of sushupti is known through arthApatti/vyatirekI-anumAna.एवमुत्थितस्य ज्ञानाभावपरामर्शोऽपि ज्ञानविरोधिनोऽज्ञानस्यानुभूततया स्मर्यमाणस्यानुपपत्त्यैव प्रमीयते नानुस्मर्यते।
Thus, present jnAna-vishesha-abhAva can be known by vyatirekI-anumAna/arthApatti/anupalabdhi. Present jnAna-mAtra-abhAva (which is only in sushupti) cannot be known by pramANa, as there is no antah-karaNa then. However, it is known by sAkshI ajnAtatayA.
Regards.
Sudhanshu Shekhar.