I'm not sure what kidnapping you are on about as I can never remember the storyline in Game of Thrones so I'm not sure how much the following is relevant.

Maximilian of Austria was imprisoned by the citizens of Bruges during the second Flemish revolt in 1488. The Flemish were notoriously rebellious but taking their lord, the son of the Holy Roman Emperor, prisoner was a step too far. His father raised an army into the tens of thousands to pressure the Flemish into releasing the King of the Romans (Maximilian).

They eventually agreed to let him go for extensive concessions on the side of Maximilian, mainly regarding the reinforcement of the Flemish autonomy in relation to their lord. Maximilian however didn't have any intention to keep to the contract and indeed didn't whatsoever. In a pretty devestating campaign Maximilian retook the rebellious duchies and counties neighbouring Flanders and finished off the Flemish last. This was pretty much the last instance of traditional Flemish rebelliousness, barring some strong disputes with Charles V (Maximilian's grandson).

I'm not sure how much this instance is comparable to the kidnapping of the noble you spoke of, but it is a pretty interesting account of "high level kidnapping" I'd say.