Client flew me JFK-FCO one way then the return ended up being booked as FCO-LHR-JFK-LHR as it was only about $100 more than the one way fare would be. Booked on client credit card and I was out about $100 of my expenses in order to balance the books.
The schedule change was relatively minor so didn't go in to the realm of EC261 but did allow me to cancel the JFK-LHR flight with no penalty.
Now the refund is going to the client credit card I am effectively out of pocket as I forfeited expenses and it will only stand to confuse them when I try to correct the issue. It would have been much easier if I got the voucher.