cant grep password in MoreKernelFiles

tried to grep the passsword in the books but it doesnt work

grep password L_txt
password
Command 'password' not found in room 'MoreKernelFiles'
grep password= L_txt

UPDATE
so it works but only if you grep the exact file and its kind of confusing when you type it out and then it just continues to the next line and doesn't exit out of the function until you hit enter again. or tell you it couldn't find it or something. I also only figured this out by reading all the books in MoreKernelFiles and finding the exact book I needed to grep, I would update this so its more clear how to do this.