Key-less start stopped working

While shopping today my car stopped recognizing my key fob for key-less entry and key-less start. It said "remote not found." I went into Office Max and bought a brand new battery for the key fob. It still wouldn't start so I now know that is not the problem. I used the manual start and got home. Upon messing with it at home, the remote system started working again! It did this last year too and I took it to the Chevrolet dealer. They put it on the computer and nothing showed. Thank you for your help!