
So I was asked in a interview what I might say if a employee was talking about taking a sick day before taking vacation and what I would do with that how do you answer such a thing?

Wow! How do you honestly answer something like that without sounding suspect or insensitive to the way the person might be feeling. We can't assume the person is lying and then take action against what we think is a lie. Do you let the person get away with the possible lie or do you believe them because they could have possibly come down with a 24 hour but or virus. I think that if the person says they're sick you have to believe them or possibly appeal to them and say we really need you for a certain project and see if they're willing to stay half a day or something. I'm sorry for this long response. I guess I should've said I'm not sure how to handle this one and just accept to believe them if they say they're sick.. I would say they would need to bring a doctor's excuse once they come back from vacation.
I would advise the employee to check the company policy as to payment for holidays. Some companies might not pay if a sick day is taken the day before. Or ... is he trying to discover if you would report the employee, rat her out for lying about a sickday?