This isn't the story you were looking for but it has a similar theme in which Dean is made to procure an item while Sam held and tortured. You may want to give it a look.
Bad Mojo By: KayValo87 The Winchesters get pulled into the middle of a supernatural land war when a sorcerer orders them to take out the competition ... or pay the price of failure. Limp/Hurt!Sam, Angry/Protective!Dean
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Bad Mojo
By: KayValo87
The Winchesters get pulled into the middle of a supernatural land war when a sorcerer orders them to take out the competition ... or pay the price of failure. Limp/Hurt!Sam, Angry/Protective!Dean
https://www.fanfiction.net/s/5771463/25/Bad-Mojo