No, unfortunately there's no way to save their translation because they operated outside of the workflow and storing methods.
It's like a developer fixing a piece of code for us but doing everything in notepad text files. Then sending over 25 text files saying please integrate these as changes to Joomla code. Sure, I guess you could do it but it would probably make some of the code maintainers heads explode. :)
This editor did not even add themselves to the translation team list where they would have gained knowledge of what to translate and then had additional support to do the translations properly.
Tom
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Tom Hutchison
Joomla! Production Leadership