Here is the Nebraska requirement from:
http://statepatrol.nebraska.gov/forms/ccw/CCWRegs.pdf
So, at what point did the contact with the police officer in the OP go from "social" to "official". What was the basis for the "official" contact made by the police officer? He sees a leather strap under the coat of a man wearing motorcycle protective gear who happens to be riding a motorcycle at the time? That is REALLY suspicious of a crime in progress meeting the requirements for a Terry Stop? Really?
Did the OP do ANYTHING that was worthy of suspicion that a crime was about to be committed, ESPECIALLY
AFTER he purchased a drink and left the premises and was preparing to drive off? IF the officer felt there was suspicion of a robbery about to be committed, why did he wait until AFTER the OP made a lawful purchase, and was out at his motorcycle preparing to leave WITHOUT INCIDENT!?!
Sorry, I stand by my judgment: ignorant cop who might have been improperly trained, forgot his training, didn't understand his training regarding the requirements for a Terry Stop type detainment, which is when notification is required in Nebraska OR maybe he was just power hungry and gets off on using his badge to harass law abiding citizens belonging to a certain group of people that he might have predjudices against.