Split forum guys I'm sorry, just looking for as much advice as possible.

Okay... my brother let me take his new 6-speed (with 600 miles on it) out to drive by myself after hours of me begging him to let me drive it. I'm going along on the highway at about 65-75 in 5th gear when I decide to downshift to 4th... ONLY , I accidentally hit 2nd and for a split second the tach shot up to what seemed like 8k rpm until I punched the clutch and threw the car into neutral. I've been too scared to tell my bro what happened (he'd kick my ass if he knew) but I'm wondering if I just ruined his car. I've heard that the rev limiter kicks in to cut off the gas but not for something bone headed like what I did to make the engine hit 8k rpm. Is there any way to know how bad I might of F'ed up the car? Please let me know if I killed his car!