Tips to keep your wordpress site updated with security :
- Make sure you have upgraded stable version of wordpress.The only way to prevent this is to have your wordpress updated everytime there is a major update on wordpress and the plugins you use. They upgrade it because the current either has security flaws or for added feature.
- You have plugins which are yet to be upgraded as well.
- Your website seems to have an outdated theme (Twenty ten) Although this template is not being used, twenty ten template attracts most hackers and must be removed.
- Your passwords must be very strong.
You can read reviews about security plugins wordpress provides and use it on your website to prevent this from happening again.
Simply restoring the wordpress pages back will not fix a hacking issue. You will need to check what caused the problem. Some of the best tips are given at : http://codex.wordpress.org/FAQ_My_site_was_hacked
There is an security scanner for wordpress at : http://wordpress.org/extend/plugins/6scan-protection/ You might want to install it and check if there is still any hacked codes present.
Unless these steps are taken care of, I would say no wordpress website is safe. These instructions provided will help your developer to get your website a secured one.