The exact same thing happened to my site. The hosting provider is Clook, if that means anything. I wonder if they're somehow to blame for this?
One thing I would do if you lost your webmaster is get a new one and use a standard theme or buy one. I use Divi from Elegant Themes for lots of our customers. Second, host with a company that not only does routine backups but can restore them for you. Third, see if you can get ClamAV installed and run a scan on your cpanel if it is linux. If Windows hosting you have problems I cannot help with or advise on. You must keep your site up to date. Of course, don't use mail poet as this seems to cause issues all over the forum on this subject. Best of luck.