If you delete a post (page) in your blog, it's a simple matter to recover the post - as long as you know the PostID. Unfortunately, once the post is gone, finding the post (page) id is not a simple matter - especially for those who would typically delete a page or post without planning. Blogger does not provide the PostID in any list, that we might save, periodically, to reference later.
The task of retrieving a deleted page or post is particularly frustrating, for owners of private blogs. Private blogs probably won't be cached, nor do they publish a blog feed - and without either a cache entry, or a feed reference, the PostID for a deleted post is not easily obtained.
Right now, once you delete a page or post, in a private blog, you're out of luck - unless you have cached the blog on your own computer. Retrieving from local cache is not an issue to be productively discussed in Blogger Support, as it is going to be as individual as your computer may be.