LEAVING YOUR SEAT H 835 "When someone gets up and leaves his companions and then returns he is entitled to occupy the seat he left." R 835 Muslim with a chain up to Abu Hurairah who related that the Prophet, praise and peace be upon him, said this.
825- وعن أَبي هريرة رضي الله عنه : أنَّ رسول الله صلى الله عليه وآله وسلم ، قَالَ : "إِذَا قَامَ أَحَدُكُمْ مِنْ مَجْلِسٍ ، ثُمَّ رَجَعَ إِلَيْهِ ، فَهُوَ أَحَقُّ بِهِ" رواه مسلم .