Does have anyone link to the reference where Robert Lucas said "market is always in equilibrium"?
I think this is a poor oversimplication of Robert Lucas's maxim. It's one thing that Robert Lucas models markets as if "always in equilibrium", it's quite another Robert Lucas claims it's an empirical truth that "market is always in equilibrium".
Lucas(1978) explained briefly why he chose such methodology which doesn't faithfully reflects reality:
As always, there are innumerable ways for the economy to be out of equilibrium, so we must expect any treatment of out-of-equilibrium behavior to have considerable arbitrariness, not resolvable by economic reasoning.