fish will often jam themselves in your rocks until they get more comfortable. So DO NOT move your rocks trying to rescue it or find it, unless you know it is dead. It is insane how small of a nook they can fit and really jam themselves into.
6 lines are known jumpers....have you checked a solid 10 ft radius around your tank, under, above, etc.
My guess is that it is just hiding. what other fish do you have in there