I booked myself a flight from BOS to RIC leaving Wed and returning Thu for personal reasons. This has now been turned into a business trip and I need to add a day to my trip. My original ticket was $210, to change the return date through Travelocity is $190 (plus tax I imagine). I don't think I can put in for a $400 expense for a ticket with work when they can just buy a new one for $200ish. Any way to get any value out of my original ticket or am I just out the $210?

What sort of fees are involved if I "miss my flight" and show up the same day of my flight but say 12 hours later?

This is US Airways if that makes a difference.