[Overdrive]

I'm wondering if the oils from your cardboard air freshener reacted with the OFT surface and deformed it in a way that seems like it melted. If they're not normally in contact with each other and ended up that way because of your glovebox being moved and the contents rearranged, could be what happened. Those air fresheners often have warnings on them not to let them come in contact with certain surfaces or materials because the oil can stain them or break them down.

Edit: Upon some rereading, it's not likely that the oil would've done that over just a few minutes, or possibly even hours. It would've had to contact the surface for a while. What I've seen from people talking about a work light may be what happened, but I suspect other plastics in the box and the box itself would've been damaged too if it were that hot.