have you tried searching using 'rule' as the keyword under Description instead of title even though using 'rule' under title should bring you quite a few.
Check which version you of trainz you are looking for. I checked all versions and got 37 hits using 'rule' as the keyword under title and 308 hits using 'rule' as the keyword under description.
I think your problem is that your keyword is 'rules'. You should drop the 's'
Hope this helps.
Mike