'Restore' and 'restart' aren't the same thing; holding the lock button then quickly pressing the up/down volume buttons is a force reset. 'Restore' means to connect it to your computer and use the Finder (Mac (10.15 Catalina or later)) or iTunes (Windows or Mac 10.14 Mojave or earlier) to restore from a backup (or format and reinstall iOS).
If your phone's lock button is physically damaged, you'll need to schedule a Genius Bar appointment at your local Apple Store and ask about repair (if it's still has AppleCare coverage, there will likely be an excess to pay, depending on how Apple determines it was damaged), if not, it could be costly.