I hate to say it, but if you look at
http://www.fedex.com/us/service-guide/after-you-ship/terms/express-ground-samedaycity.html
and go to "liabilities not assumed"
Section AG: Shipments released without obtaining a signature at nonresidential addresses when release has been authorized by the shipper or recipient. (See the Delivery Signature Options section.)
I know it sucks man. Personally I hate when people ship me things with signature required, but I understand it, and whenever I ship anything over $100 I require a signature.