The reason players get staked is because they do not have the initial capital to invest. When a player ships an insane amount of money, there is no need to seek future staking capital from the initial backer.
A horse will only ship funds back to the backer if he seeks to benefit by having future staking opportunities. In this case, the horse no longer needs the backer, so it is illogical to ship any funds at all.
Your argument is that well, "we struck an agreement and now he is not paying up" .. Damn straight he isn't why the hell would he? Let's do a cost-benefit analysis here..
By him shipping you $115k his bankroll takes a -$115k hit
By him keeping the $115k, his bankroll remains at $230k
By him keeping the $115k, he loses future backing opportunities from you which he no longer needs. Your use value has dried up.
Now one may suggest, that what JackQKA did (if true) is unethical, immoral, scum etc.. Here's a lesson in business.. Business has no ethics, morals or virtues.. There is no such thing as the right or wrong; there is no such thing as good business. What it comes down to is maximizing ones potential profit at any cost. In this case, the cost of chincing you on your piece of the pie has substantial benefits.
Money is the root of all evil, don't act surprised. His greed is in conflict with yours. For if you were in his position, I'm sure you would do the same thing.