I'm doing a critique of an Economics paper, and I want to have my critique about omitted variable bias. I have found a variable that was not included that is both correlated with my regressor of interest (The covariance does not equal 0), and is a determinant of the dependent variable (its coefficient is significantly different from 0). However, by including this omitted variable, it causes the coefficient of my regressor of interest to become statistically insignificant at the 5% level. Whereas, the coefficient on my regressor of interest was significant at the 5% level before the omitted variable was included.
What does this mean? And is this still omitted variable bias given the change in significance?