Comment by mesrik

OK, I found bit more from UNIX System Administration Handbook Third Edition (Evi Nemeth, Garth Snyder, Scott Seebass, Trent R. Hein, with even more authors mentioned) 2001 book following:

  "134 UNIX System Administration Handbook
  ...
  The lost+found directory is automatically created when you build a filesystem. It is 
  used by fsck in emergencies; do not delete it. The lost+found directory has some
  extra space prealocated so that fsck can store "unlinked" files there without having
  to allocate additional directory entries on an unstable filesystem. Some systems pro-
  vide mklost+found command that can recreate this special directory if it is aci- 
  dentally deleted.
  ...
  "