you have a potential problem. If you no-show the first segment, all the other legs on this booking automatically cancel. You also don't qualify as an "open jaw". because your origination and return cities are too far apart. Basically, you now will have a point to point ticket. It's probably a good idea to go right to Customer Care and explain what happened. This is a ticket that could become very expensive. You might be better off buying a new one, and reusing this with a change fee on some other trip.