Photos missing after update

Please help! Today I upgraded to Lightroom 7.0, no issues, later I am back on lightroom editing photos. All of a sudden half of my photos just disapear! No idea where they have gone, how do I get them back? 

I can always reimport as I have the original files but all of my hard work and time spend editing is gone! I'm devestated. If anyone can shed any light onto where they have gone & how I can get them back it would be much appreciated!

(The photos are not 'missing' as many other discussions discuss they have literally just vanished!)