I have suddenly stopped getting snippets as part of Visual Studio IntelliSense, which was very unpleasant, as I have some in muscle memory. Luckily the problem can be resolved quite easily. In Visual Studio, go to Tools - Options. Go into Text Editor - C# and select the IntelliSense section. Now check the Snippets behavior group and you may see that Never include snippets is checked. Switch that to Always include snippets and your snippets should be back!
I still don't know why the setting switched to Never in the first place but I am leaving this here for future reference :-) .