I've over 10 windows of a file manager (Thunar, on Xubuntu Core 18.04) open, but ps aux|grep thunar shows nothing (except for the grepped string). Why? ps -e doesn't help either

EDIT: I suspect a reason may be that the location (in the address bar) in those windows is an ejected external media. Another one may be that I didn't open the windows (they opened automatically when I plugged in the media), so the processes might not be mine. However, this still doesn't explain thunar not showing up. The problem persist after logout