To the best of my knowledge there were five or even six passions attributed
to JSB:

1) Weimar Passion? BCD1- music and text lost;

2) St John Passion BWV245 (or BCD2a-e)- in 4 versions & 1 unfinished
revision;

3) St Matthew Passion BWV244 (or BCD3a-b)- in 2 versions;

4) St Mark Passion by R Keiser with Bach's contributions BCD5;

5) St Luke Passion by an anonymous author with Bach's contributions BWV246
(or BCD6);

and 6) St Mark Passion by Bach for which only text survived BWV247 (or
BCD4).  As far as music is concerned most of it survived in the Trauerode
'Lass Fuerstin' BWV198, besides a few movements were used also in some
other cantatas.  There were already a few successful attempts to recreate
the piece and I believe that there are some recordings around.  For
thorough information I would recommend the book:  G.A.  Theill - "Die
Markuspassion von Joh.  Seb.  Bach (BWV 247):  Entstehung - Vergessen -
Wiederentdeckung - Rekonstruktion" (Steinfeld, 1981).

But there were also some movements from Passion pasticcio after C.H. Graun
BWV1088 (or BCD10)

Hope it helps.

Pawel Kotla