It's in the .css of their site, kind of: https://www.visitkingsisland.com/css/screen.css
This line was commented out:
/*.m2014-microsite #marketing .container .leftborder.internal, .m2014-microsite #marketing .container .leftborder{ background: url('/images/purple/border-panel-left.png') top left no-repeat; }
.m2014-microsite #marketing .container .rightborder.internal, .m2014-microsite #marketing .container .rightborder{ background: url('/images/purple/border-panel-right.png') top left no-repeat; }*/
This was the fake one:
.m2014-microsite #marketing .container .bottomborder{ background: url('/images/structure/border-panel-bottom-2014.png') top left no-repeat; }
I assumed there had to be a border-panel-bottom.png in the /purple/ directory. And sure enough, there was.