Please help in simple language, I'm not a techie. 
At least twice in the past month my DataPoint v 6.1.0.40 (64 bit)session/window closed while a query was running. No error message or anything, the entire window just disappeared. The first time I assumed I had accidentally closed it but I just saw it happen and I know it wasn't something I clicked. It does allow me to recover the file when I re-open a session.
Please, please open a Support case for this/such incidents... something not obvious is happening under the covers, and may require support to give a Support bundle from your TDP to Quest's Dev team.
You can open a support ticket here...