I think I get what you are asking.. ?

sick this in ~/bin/musthave and chmod 0755

#!/usr/bin/perl 
use strict;
my ($what,$file)= @ARGV;
open(HANDLE, $file);
my @match = grep { /$what/ } <HANDLE>; 
close HANDLE;
scalar @match or print STDERR "$file is missing $what\n";
exit;
[download]

then do ..
 $ find /where/my/stuff -type f -iname "*txt" -exec musthave 'I WANT THIS INN HERE' '{}' \;

What I like doing with these little things that are useful and may be used on one or a thousand files.. is to isolate the problem to *one* file, and use the system to call it multiple times (or antoher script to iterate) as needed. That way you isolate the problem into smaller parts.