Are "no work" holidays supposed to take away my work vacation days???

Another update. My sim celebrated WinterFest, and gained another vacation day.

So, I don't know what happened with the OP's game, but in my game -- the untouched built-in holidays do not appear to use up vacation days.

Edited to add: I guess it's possible that he would have normally accrued 2 vacation days instead of 1 that day; I never had paid attention to the rate of vacation accrual. My sim is at level 6 in the Business career.