I lost a tag from my first set too. Replacement was quicker than new kit (I crossed 50K on the same flight I lost the 35K tag, and had the replacement tag a month before the new kit). I got them via a simple tweet request.
It is bad design. The hole is too close to the edge and is too small, the fastener is too easy for someone other than me to mess with (and I worry it will undo itself), and the wire is slightly abrasive if rasped against the edge of the hole. If the wire loop stays round, the tag will freely float and not stress the hole in the tag, but each time I have put a new tag into checked bags, I always find someone has pinched the wire to make a V, or pulled on the tag hard enough to kink the wire, and this is unlikely to have been done by the laws of physics, so it seems someone is taking it upon themselves to handle the tags while under airport control. Grrr.