You have two different points here:
1) has the gift card has expired after one year?
2) can the gift card can be used at a different location?
For #1, see Nebraska Legislature Revised Statute 69-1305.03:
A gift certificate or gift card subject to an expiration date shall
contain a statement clearly and conspicuously printed on the gift
certificate or gift card stating the expiration date. The statement
may appear on the front or back of the gift certificate or gift card
in a location where it is visible to a purchaser prior to the
So the expiration date must be printed on the gift card. If there is no expiration date, you can reasonably argue with the restaurant that the card hasn't expired, but that is not stipulated in the law; it's simply something to argue with the restaurant.
For #2, this depends on the terms and conditions of the gift card. Is this location limitation printed on the card? Is it posted in the restaurant? If there are no written or visible limits on the location of usage, you can reasonably argue that the card should be used in any location because that limitation was not expressed in the beginning.
If there is no expiration date and no terms regarding the use at different locations, it sounds like the ramifications of giving gift cards wasn't clearly thought out by the restaurant.
You can argue with them; give them a bad review on Yelp; or take them to small claims court.