Menus in Left Panel Dissappeared

Environment : XWiki Enterprise 8.4

Another administrator of ours accidentally clicked "Delete" of Gear menu in the left panel on the main page, then 
1) the menus in the left panel cannot be recovered,
2) the design of our main page changed,
3) it is guided to install administration package, and
(e.g. The administration application is not installed. Since Xwiki Enterprise 1.5 the Administration is distributed as an application. You can download it from url...)
4) our editor was changed.

I am not sure if this is related to XWIKI-15388,
but would it be possible to recover from database table "XWIKIRECYCLEBIN"...?

Please kindly and generously help.