in Window 10 just after LibreOffice upgrade to 7.1
I presume Calc file in recent document means embedded Calc object in Writer document. If Writer still open then undo in Writer until recovered. If Writer already closed, do not re-open file with deleted Calc object. Look in File Explorer at your backup path to see if a Backup has been made myfile.bak I think. Default path
%APPDATA%\libreoffice\4\user. Copy x.bak to another location, rename to newx.odt and open.
Undo in File Explorer if deleted from there. Look in Recycle bin.
Possibly you mean that you have deleted it from recent document list? then just open it using File->Open, or using file manager…