Sorry, but I have no solution to offer for that. The search index uses apache lucene, it does not index punctuation, content is tokenized into words, searching on words will return documents that contain the word. Actually in lucene query syntax a colon has special meaning to identify the field in the index that you want to search, though this is not normally used because users don't know the field names or have any knowledge how the index is structured. But, for example there are fields named PageName and ModuleTitle.
So searching on this site with PageName:Download finds the download page.
I don't have any easy solution to offer to change the way this works. One should search on words not on strings that contain words and punctuation for best results. The help link next to the search also has info about advanced query syntax.