Ex- CS agent here...never heard of "Trip in vain." (Heard of many that fit this category, but it is not a common airline term. "Flat tire rule" is common airline term. Most of the time, I have seen agents waive all rules and let you return from an intermediate point, and let customer relations deal with the details, as nowhere in the contract of carriage is any such thing mentioned. COntract is to fly from point A to point B, and nowhere is on time even insinuated. On the other hand, good costumer service in bad situations is important, to imply that this provision exists in any written form is not a true statement. Who would the airline compensate more...the person who bought a $198 ticket to get to their wedding/ funeral that get missed, the business person who paid $1000 to get to the meeting that may influence a $100 million deal, or the couple on a 2 week cruise out of LA that's first port of call is 3 days out?

The contract does not care about what you are doing at the destination, the contract only cares about getting you there (and tries to do it as booked.)

Sorry it didn't work out though...souds like you rolled with the punches pretty well though.