If you are able to track or follow the sellers contact info or twitter handle. Send them a link with the pre populated link of how their offering could look using your service. Owler.com has an interesting way of tweeting out someones competition that way if the owner of a specific startup is tracking their brand they are drawn to their pre built link....your product could resemble this tactic. In essence you plant a seed and if the rightful owner sees it, then they may claim it. Show it built first, then sell it ;)