hi guys,
my brother wrote a check for a co. and his friend had also written a check for the same co. and offered to drop off my brother's check, along with his in person. later on, brother found that his friend cashed the check rather than turning it in. What kind of recourse can he take now? please help/advice. thank you!

If your brother have a copy of the check, take it to his bank and make a fraud claim. They may also ask you to file a police report. Make sure you follow all of their instructions.