Definitely not a goner! I have grown many coleus plants and a few have looked like yours does but recovered. They are extremely resilient!
What went wrong? Well, it could just be transplant shock. When you repotted it, did a bunch of its roots rip out? If not it could still be transplant shock, just keep it watered and it will recover (maybe give it a little extra shade until it recovers). The only other thing it could be is over fertilizing (wilting like this in coleus is usually from under watering, transplant shock or over fertilizing). If you fertilized this new pot right after transplanting the coleus, I would recommend flushing out some of the fertilizer. The transplanting is rough enough on the plant, too much fertilizer will prevent the roots in shock from getting any water and the plant will wilt.