OK so its a new environment for me and silly me - I was not yet running under source control :-((.
Last night I had made some last-minute changes, compiled and flashed my test code.
This morning the Particle Dev Atom IDE was still open, I made a couple of minor tweaks to my main CPP and H files and tried to save them. The dot just remained blue whatever I did.
Restarted the IDE and my CPP and H files are now totally empty - YUP zero bytes :-O.
SO - are the files used for the last on-line build cached on your build server under my login maybe ???.
If so this will be a life-saver (well save me recreating from scratch !!!).
If so or not - there seems to be a problem with ‘Particle Dev’ - in that it just trashed my files in the first place :-((.
Hope someone can point me at a server folder ???.