We report optical observations of the VY Scl star BZ Cam during its previous optical low state in 1999/2000 .
We find drastic variations in the line profiles .
Narrow-band imaging observations show that its nebula extends farther than previously known and seems to be composed of two components .
We determine the [ O III ] line intensity of BZ Cam ’ s nebula to 4.8 \times 10 ^ { -13 } erg/cm ^ { 2 } /s .
We discover a proper motion of BZ Cam of 25 \pm 2 mas/yr which together with the systemic radial velocity yields a space velocity of 125 km/s .
We re-interpret the nebula as being photo-ionized by hypothesized transient , luminous , supersoft X-ray emission during optical low states , and shaped by the transverse motion of BZ Cam .