A comparison on two searches and I found the following confirming that this Search Box for Blogger still is not good. The problem is probably not so much related to this Search Box (on the right side of this blog) but it's all Google and the blog search should really be fixed. Being one of the largest search companies Google should have fixed this a long time ago.
18 found using Google Search (the result includes the monthly archives) compared to Google Blog Search that only finds 3 out of 9. That means a lot of the posts are missing on this search and other searches as well. The index is obviously very incomplete and needs to improve. Searching within Blogger 9 posts are found and is the correct.