Some ways non-existent pages end up in Google's Index
There is 3 ways that non-existent pages can end up on Google's or any other search engine for that matter and these are:
Your pages are linking to these pages. (This can be in sitemap, a profile page, a blog comment or a href based a link...) I've seen some plugins from WordPress for example that contain such links because they have been developed on one site and then uploaded to the plugin library but the developer has a cache setup that has came across with the plugin.
A backlink is pointing to these pages.
I've seen Google index pages and strings that simply don't exist, though yours seems to have words that I don't see how Googlebot could come up with them.
Now it's most likely a internal link of some sort because I Google'd your title pages and all I found was 3 pages, Pro Webmaster, another site that images this site and yours. So it looks like someone has created this link, or a application/plugin/malware has.
So to rule out that your users, yourself or an application has created these links what you need to do is login to the SQL (ideally PHPMyadmin) and search for the strings.. Ensure that the database is clean of these pages.. Then assuming you get no hits its time to search cache files, and php files for these pages. If you find nothing then its likely because someone linked it too you and now its not on Google because its been removed.
/? String can be harmful if someones out to get ya
Now I can see you have removed all
/?title=strings and redirected them to home page, while this is a OK thing to do, it also can be harmful at the same time and I'll explain..
If someone is spamming your site with nasty backlinks the worst thing you can do is start redirecting them to the home page, as Google may see this as manipulate of pagerank. This is because 301 redirects the flow of juice from the external link, if that links happens be a Viagra site then your giving a false indication to Google on the redirect and this can come back and bite you.
Got to love the good old 404's
The right thing to do on pages that simply don't exist is to use a 404, these are perfectly normal and no way does it give Google the impression your site is broken. Any pages that don't exist will never end up in Google's index and anyone back linking to non-existent pages should not harm your site if a 404 returned, however as mentioned a 301 to home page 'MIGHT' because its retaining the juice.
1-2 Years ago I would say string redirection was the best method but since Google's Panda, and Penguin updates I've seen sites trying all sorts to try and damage the online reputation (Basically Panda, Penguin punishes sites for spam backlinks, paid links and generally non relevant links) Even though Google claim that it's impossible to damage the reputation of others online it raises the question if this is true why are so many currently spamming others and how do they know its not the webmaster trying to manipulate their own rankings? a debatable area but let's wrap this up... I believe a 404 will suit you best in this situation.
Editing the query should be straight foward, rather than redirecting to
/ have the string removed then 301 to