Curious Case of Polybag Sold Separately in ~2003
Air holes always seem dangerous when there's a possibility of small Lego pieces that could be forced through.
North American Lego stores used to sell these bags, but stopped in roughly 2010 due to health concerns regarding sanitizing (so I was told). They were, as yours were, just leftover bricks. I realize they don't match your description of air holes or a number, but thought they might jog someone's memory.