Can BV be positive from cervical swab, but negative in vaginal swabs?

I've had excessive yellow discharge for YEARS now. Doctors have swabbed me before and done wet mount tests (looked under microscope) and I've always been negative for BV. However I just had a CERVICAL swab done, and it came back positive for gardnerella.

Is it at all possible that years of tests could have missed BV?

Is it possible for BV to only exist in the cervix but be undetectable in the discharge?

Or is it more likely that the BV that was recently detected must be unrelated to years of excessive watery yellow discharge...