We have any employee that is in a salary position as a salesman. He occasionaly will travel for business and occasionally work a little overtime (maybe a 1/2 hr or an 1 hr per week). He normally is in the office Monday through Friday 8 am to 5 pm. He already used all of his vacation and sick time for the entire year. He recenty missed worked per personal reasons and was not paid for the time lost. He is upset because he feels that if he is salary he should be guaranteed a full paycheck even if he is not here. Can someone tell me what is the correct thing to do in these cases?

Nope, Your company has a written policy for paid time off that includes sick days, holidays, personal days, vacation etc. Once all those things have been exhausted, then he has to take unpaid leave.

Depending on the value of the employee, the company could offer comp time for travel or other OT.