Re: Ever happen to you before?
Considering the vast quantities that the big string manufacturers actually produce each year, it's bound to happen every so often. Even with the most stringent quality control measures, I imagine at least a few packs per year come out that are missing strings (or that have similar mistakes; I've never had a pack that was technically missing a string, but I have had at least one pack that had a duplicate string in place of another one...two .009's instead of a .009 and .011).
I'd be interested to see the stats from a big maker like D'Addario, though...what's their acceptable margin of error...something like .05% of all of their packs have a mistake, I imagine.
But yeah, the retailer should just crack open another pack and give you the missing string...they can always relegate the remainder to their pile o' spares (every shop has a pile o' spares).