Well the first thing I'm wondering is whether the box was sealed? Usually you expect to have maybe a third of a charge the instance you open the box, batterys can empty over time but I'm not sure it's been long enough for that, even if it was from first batch.
A retailer may reseal the package even if it was a return though, but would be obvious of it wasn't sealed.
Usually retailers are legally obliged to state if it's a return/refurbished product, although some have been known to not do so.