User blog comment:Valferys/Missing arrows/@comment-5450493-20140102183536

That happened to me once. I had 1500+ steel arrows and they all disappeared. I retraced my steps and as it turned out I had been arrested by some city guards and ALL of those arrows were marked as stolen because I had stolen half a dozen of them sometime in the past. At least I could reload that savepoint and avoid arrest again.

So maybe it was that or maybe you accidentally sold or dropped them. Good luck finding them but if you can't this sounds like a good opportunuity to craft some new arrows and level your smithing skill.