Non files displayed in the project list

Hi to everyone!

After creating a project and treating it like a single file to translate, the system doen't open the window for project setting but immediatelu opens the file itself for translation. Then, once this file is closed, I cannot find it again in the project panel list. If I open indipendently my File Manager I can see that the sdlxliff is there (path: ...Studio 2017/ projects/dorp files) but there is no trace of it within Studio (2017). Have you any idea of where and how can I find it? My workaround has been that of loading the same file as a Project but I would like to understand why this  happens if it is treated as a "single file" (it happened already twice). Thank you veru much!