I've found out with one file, that when I run this command:
sketchtool export layers file.sketch --items=<id to search> --use-id-for-name --output=<folder to output> --formats=png
it searches for layer with id "<id to search>" by checking "originalObjectID" layer property, instead of "do_objectID" one. Is it expected behaviour? And if so - I've also found that "originalObjectID" is not unique, how can I tell which layer I want to export?