There doesn't appear to be a way to search just "My Books". But... it seems to display all the book titles on one page (at least when I do a regular search it shows 100+ books on one page). I suppose you could just CTRL+F and use your browser to search the page.
I don't plan on putting that many books into Google Play. I keep all my books in Calibre and just load a few I plan on reading. When I'm done, I delete them and load new ones. I can't read 1,000 books at a time anyway.
