Sounds like OP didn't actually make any mistakes. The bags never made it out of Barcelona. That was AC's fault, not OP's fault.

OP, what sort of interim expenses? Was WPG home for you, or was it an outbound stop? That may make a difference in terms of what they'll cover, since it's easy to claim you need emergency stuff when you're on the road, but harder to claim you don't have a change of underwear or clothes if you're back home.