I had a look to see if Bolivia has a law similar to EC261 and it actually does. It's covered by their transportation ministry, ATT, and you can make a claim via their Odeco system. The complication will be that OB will probably say they only delayed you by 20 minutes on landing, and the rest is not their problem, but theoretically on a single itinerary ticket, they might have duty of care obligations and to reimburse you 25% of the ticket cost, as you were delayed over 6h to your final destination. All this is in Spanish only - the claim form and all the rights info can be found here.

I imagine you will end up with OB and IB blaming each other and you getting nothing, but your best bet is probably to get one to put in writing why the other has to pay up (IB would need to state that OB informed them of a definitive delay beyond MCT or realistic conformance time, or OB would have to state this was not the case and IB handled you incorrectly), and then use that to try and have them do so. Going to be marginally easier pursuing things in Europe with IB, I'd imagine. Good luck!