I had similar problem when i rezzed a box. I was wearing wrong tag and the box didnt appear on the ground like it should, So i thought i would find it back to my inventory but it was missing also from there. I relog and the box reappeared in my inventory.
If i were you and the box wouldnt be able to find in my inventory i would demand from the creator to send me one back:)
You paid it, you deserve to have it