Forgetting the details is part of the test of worldly life. Yet the traces and teachings of the Day of Alast (the Realm of ذرّ) remain within our hearts—in our primordial nature. It is like someone who has forgotten the memories of primary school but still retains what they learned, and may one day remember it all.
For further study, consult the commentaries on verse 172 of Sūrat al-Aʿrāf:
الأعراف : 172 وَ إِذْ أَخَذَ رَبُّكَ مِنْ بَني آدَمَ مِنْ ظُهُورِهِمْ ذُرِّيَّتَهُمْ وَ أَشْهَدَهُمْ عَلى أَنْفُسِهِمْ أَ لَسْتُ بِرَبِّكُمْ قالُوا بَلى شَهِدْنا أَنْ تَقُولُوا يَوْمَ الْقِيامَةِ إِنَّا كُنَّا عَنْ هذا غافِلينَ
“And [remember] when your Lord brought forth from the loins of the children of Adam their descendants and made them bear witness concerning themselves, [saying,] ‘Am I not your Lord?’ They said, ‘Yes indeed, we bear witness!’ [He did this] lest you should say on the Day of Resurrection, ‘We were unaware of this’—that is, unaware of the primordial covenant of divine unity.”
ٍ عَنِ ابْنِ بُكَيْرٍ عَنْ زُرَارَةَ قَالَ: سَأَلْتُ أَبَا عَبْدِ اللَّهِ ع عَنْ قَوْلِ اللَّهِ- وَ إِذْ أَخَذَ رَبُّكَ مِنْ بَنِي آدَمَ مِنْ ظُهُورِهِمْ ذُرِّيَّتَهُمْ وَ أَشْهَدَهُمْ عَلى أَنْفُسِهِمْ أَ لَسْتُ بِرَبِّكُمْ قالُوا بَلى
قَالَ ثَبَتَتِ الْمَعْرِفَةُ فِي قُلُوبِهِمْ وَ نَسُوا الْمَوْقِفَ سَيَذْكُرُونَهُ يَوْماً مَا وَ لَوْ لَا ذَلِكَ لَمْ يَدْرِ أَحَدٌ مَنْ خَالِقُهُ وَ لَا مَنْ رَازِقُه
Al-Maḥāsin, vol. 1, p. 241
Ibn Bukayr narrates from Zurārah that he said: I asked Imam al-Ṣādiq (peace be upon him) about the words of God Most High: “And [remember] when your Lord brought forth from the loins of the children of Adam their descendants and made them bear witness concerning themselves, [saying,] ‘Am I not your Lord?’ They said, ‘Yes indeed, we bear witness!’”
Imam al-Ṣādiq (peace be upon him) said:
“Knowledge [of God Most High] was firmly established in their hearts, but they forgot that moment [when they bore witness]. Yet a day will come when they remember it. Were it not for that Day [of Resurrection], no one would know who their Creator is or who provides for them.”