Can my employer refuse to pay me for the last week I worked?

My Indiana employer paid me salary, and I have a signed contract. On my paystub it shows an hourly rate times number of hours. When I quit my supervisor only paid me 40 hours instead of the regular 80 hours for bi-weekly pay. She stated it was because all the work I missed. I only missed one day during the last pay period, plus I worked one day on the next pay period. Is she allowed to arbitrarily decide how many hours I should be paid? I worked at an apartment complex and was the only person in the office. There were times I had to be out of the office for business reasons and she says she was told I was never there. There are several documents, faxes, Skype messages and emails to prove I was there every day but the one day I missed. Is this legal?