I logged off the game this afternoon, nothing unusual. Came back to play and the launcher is missing from the "recently opened" menu and I can't find it on the computer at all. Using an iMac from late 2015 running el capitan 10.11.5.
Searched the forums for information on this and found only references to this problem from 2014 on a PC.
No problems prior to this except that some of the sound effects had stopped working - people have already posted about that issue in other discussions.