I've seen problems with other items too. In one of the battles it said there was like 97 throwing left but if you picked it, you'd spawn without them and the equipment box stopped handing them out.
It's also fairly common to put stuff in the equipment box, look in there later, see "1 elite scimitar" or whatever, select to use it and it won't give it to you -- you also can't spawn with it.
I assume these problems are tied to people taking things out of equipment boxes (or maybe putting them in) but I dunno for certain.
Can't recall seeing this happen with armor, either -- just hand-held items.