files disappeared

[Linda]

I am using Lubuntu 14.04.2.  I was looking at a file in a 
directory earlier this morning and everything was fine. Then 
I went back to check something and every file has 
disappeared from that directory.
They do not appear in Trash and they do not appear in the 
terminal window with a ls -la, however they do appear with 
locate. They also don't appear in recent opened files in 
Libre Office even though that is what I looked at them with. 
Any ideas how or why they disappeared and how I can recover 
them?
                        Thanks
                       Linda