Staff does not delete characters under any circumstances. Make sure you're logging into the right account that has your characters.
To verify what accounts you've logged in on your computer and what characters are under said accounts, follow the steps in the sticky thread:
https://forum.nostalrius.org/viewtopic.php?f=45&t=11569FAQs > "How can I find out my account name?"
Browse to World of Warcraft Classic\WTF\Account folder to see all your accounts. Open each account folder up and open the "Nostalrius Begins" folder to see all you character names folders.