Having an issue searching for a string in a file

There seems to be an 'in' missing in the line with the case statement as well as a closing esac:

echo "Do you wish to search again? [y/n]"
read INPUT_STRING2
case $INPUT_STRING2 in
   y)
   ;;
   *)
   exit
   ;;
esac

You did two syntax errors (in after the variable and esac as end of the case statement):

echo "Do you wish to search again? [y/n]"
read INPUT_STRING2
case $INPUT_STRING2 in
   "y")
   echo "Searching again"
   ;;
   *)
   exit
   ;;
esac

I want my script to tell the user if the string isn’t found ….    I have tried ... to use an else statement but it didn't work.

What did you try?

if grep -q "$STRING" "$FILE"
then
        echo "string found"
else
        echo "string not found"
fi

works.

P.S. I advise you to quote all references to shell variables (e.g., "$INPUT_STRING2", "$STRING", and "$FILE") unless you have a really good reason not to and you’re sure you know what you're doing.  Conversely, you don't need to quote constant strings (e.g., string found) unless they contain special characters.  (Square brackets – “[” and “]” – are special characters in this context.)  But it’s a good idea to quote them anyway.