You could also use $file(filename) as well. It will return $null if it is not found or 0 if the file is empty. You could even test for both conditions if you wanted to.
on *:TEXT:!exists*:#:{
if ($file($+(",$mircdir,$$2-,.txt")) == $null) msg $chan $2 was not found.
elseif ($file($+(",$mircdir,$2,.txt")) == 0) msg $chan $2 was found, but it's an empty file.
else msg $chan $2 was found!
}
You could also use:
msg $chan $findfile(C:\,$+(",$2-,.txt"),0,msg $chan $nopath($1-) was found in $nofile($1-)) matches found for $2-
but that's getting a little out of hand, don't you agree?