I had some serrated arrows equiped and regular arrows in my alt slot. then I bought some more regular arrows and drag and dropped them to my alt slot and I noticed my alt slot arrow pile didn't go any higher. After awhile of playing around I noticed my main arrows slot on my character was arrows and not serrated arrows... soo some how drag and dropping got rid of my serrated arrows, just deleted them I believe.
also I think dieing on an elevator and hitting the switch refreshes the corpse decay timer, like picking up an item and dropping it again in another location.
Are you sure you didnt run out of serrated-arrows.... Generally the game will place arrows into your pack when dropping on your alt-slot.
Followup: I did confirm this is the behavior of the arrows, they fall to your pack or combine with what you have equipped as primary when dropping on the alt slot.