Olá! Aw that’s difficult about the physical address.
I think perhaps you could write to Scholastic customer service, and ask if there is an email address that you could send an email to? https://www.scholastic.com.au/about-scholastic/contact-us/
customer_service@scholastic.com.au
I did see that address on her website from a post in 2015:
"If you want to contact me, the best way is still to write to me care of Sarah Hatton, Scholastic Australia, PO Box 579 Lindfield NSW 2070 Australia."
http://www.emilyrodda.com/2015/08/01/welcome-to-my-new-look-website
That is from Scholastic Australia and I’m not sure if she’s still publishing with them. The latest thing on her website is 21st edition of Deltora quest with Omnibus books which seems to be under Scholastic.
I am in Australia actually but not sure if I can help, if the address and person may not be the same.
I think the best thing is to check with Scholastic Australia the publisher, and see if there is a way to send fan email. Maybe they can forward it for you