The band was forced to scrap a show at the Grand Metropole Sao Paulo on Thursday (03Apr14) after the singer lost his voice in rehearsals.
He was ordered to rest before the group's headlining set in the same city on Saturday, but Bellamy admitted he was struggling to recover.
After the Lollapalooza gig, he tweeted: "Thanks Sao Paolo (sic) for ur support tonight and singing for me. Sorry we missed Muscle Museum. promise to come back next year and will play it."