It really amazes me how petty some people can be. A GS spends tens of thousands with UA every year, or at least his company does, and the fare paid for this ticket is likely pretty high in the hierarchy. Why is paying another $25 such a critical matter for this person/company? Most credit cards would cover this as part of the trip interruption insurance, or ancillary travel insurance that all road warriors should have. (Not only that but had OP been a SPG elite, he'd have had reciprocal elite benefits on DL.) Furthermore, how would the GS agent authorize payment of the luggage charge on another airline? Would this not be something to deal with via GS customer service after the fact? Indeed, has OP not contacted them to see what they might offer in compensation?