My master bus disappeared from my mixer.

[Gone To Lunch]

The sound comes out as it should, but it is not present in the mixer?

Presumably I must have deleted it accidentally, so how do I get it back?

[Dietz]

Just create a new bus, assign the proper physical outputs and route the other channels to it. You can also call it "Master Bus" again, to make life easier. :-)

BTW: The fact that you can still hear your instruments playing leads me to suspect that you may not have used the disappeared master bus at all, or at least not for all channels, but assigned them (some) directly to the output.

HTH,