Jassa, maybe you haven't studied history, but 1699 accounts do exist. That too from that time.
Its not because Sants or Scholars don't mention them that they don't exist.
Sants mostly read from Granths such as Dasam, Sarbloh, Suraj Prakash, Panth Parkash (new + old), Bansawlinama etc or Rehatnamas.
New manuscripts are being discovered in libraries, with Sikh families etc.
I don't say this account is true, I heard same claim that there is no Aligarh manuscript, but to say that they (1699 ones) don't exist is not a wise thing to do.