so no APE tags? too bad.
You could examine one of the files for which you know that it must have the traktor field with MP3diags (see here for a link: How to check files for errors?)
This does not mean that the file is broken but MP3diags may show you all the tag fields with their 4-letter-token. It could be that you find a field token called PRIV - this would be a private field that only traktor could read and which has a binary content and is not supported by MP3tag.
If you do not find anything like it, then it is unlikely that traktor has written the field.