Silverfist quest weapon skill book not dropping in cruel act 6

Hi, I killed the Silverfist side boss in act 6 which dropped a weapon skill book. I went in maps and accidentally dropped the book in maps which made the book disappear. I decided to redo the quest thinking the book would just redrop but now the Silverback in not dropping the book anymore. I know I didn't read the book because I only have 22/24 weapon skill points and I already completed every other quest in campaign. I also waited 3 hours for the instance to clear up still nothing. Please help!