In Confluence exists a page with the title "Fritz!Box". If this title is entered in the quick search it brings up that page. If the real search is used (searchisite.action) it doesn't bring up that result. If the exclamation mark is escaped with a backslash the site is found.

The search box seems to not escaping those special characters when jumping from the quick search to the real search.

Workaround:

If the page title contains any of the special characters, you need to add \ before that character and you will see the search result.

So in this case the search should be :

 Fritz\!Box