I would assume it would depend on how you get vacation time.
For example, at my company, we “accrue” a certain number of vacation hours per pay period. When we take vacation time, we can’t use up more than what we have banked (at least not without some management approval). Should I get fired or quit, those banked hours gets paid to me on my last paycheck. If I was negative, I would almost certainly owe them.
If you get alloted a certain number of hours in a lump amount to last for the whole year, you may owe the company for the days you took if you used up more than 1/3rd of them since you worked for 1/3rd of the year after getting them.
How much vacation had you earned, how much did you use, and how long was the work period the final check covered?
The best suggestion I can come up with is to speak with your ex-company’s HR department, have them show you the pertinent parts of the employment contract and/or employee handbook regarding vacation accrual and what happens to time used/not used if you get terminated.