Using Ubuntu 18.04 with Unity desktop. Have been doing so for a long time; have not recently installed or changed anything. I just restarted the computer after it became unresponsive and started telling me that it couldn't find a default application to load certain basic files. Upon restart it popped up a dialogue box to say that the Downloads folder is missing, (as it is contained within the pictures folder). Everything else seems to be fine, but Pictures has gone completely AWOL! As it turns out, it appears to be intact in the rubbish bin. I did NOT put it there! When I try to restore it, it either says there is not enough space to do so, or if I try to copy it to an external drive (upon which there definitely is enough space) it says "Items in the rubbish bin may not be modified". How the blazes do I get it back??
Ta!
~/.local/share/Trash/files
and copy the ones you need to another place (mount point) with enough disk space.