OK. Done some testing now, different variations. Conclusion is simple: if you let windows store recent items, also the hidden files are shown in search results
even if the "Recent Items" menu is not shown in Start Menu.
To be sure no hidden files are shown in searches you have to uncheck both of these choices:
1. "Store and display recently opened items
..." in Taskbar properties > Start Menu
. Here you decide if Windows is allowed to store a list of recent items or not.
2. "Recent Items
" in Taskbar Properties > Start Menu > Customize
. Here you decide if the above mentioned list is shown in Start Menu. If you have unchecked the choice above but leave this checked, the Recent Items menu is shown but always empty. If you uncheck this but leave the one above checked, your hidden files are still shown in search results
In my opinion this really is a bug. If I choose to hide a file, it should absolutely not show in search results. It would be far better to have for example a control panel item for search options, where I could choose if I want to include hidden files in my searches.