What are the signs that someone has become enlightened in Buddhism? Have there ever been any cases of people disappearing after becoming enlightened?

In Buddhism, there are “Seven Factors of Awakening” that show enlightenment:

• Mindfulness: To maintain awareness of reality, in particular the teachings of Buddha. Reality in this sense means staying in the Here and Now. This is in contrast to our minds fearfully and restlessly running from the past to the future and creating and inner and outer atmosphere of fear and stress.
  
  

• Investigation into the nature of reality. This means looking within and finding our connection to Cosmic Consciousness, the underlying organizing intelligence of the Universe. It does not take the objects of our physical perception as being the true reality. It means living a life of contemplation into what is behind the illusion, instead of taking things at face value.
  
  

• Energy. This means determination and effort to move beyond the endless stream of activities and thoughts that we take as daily life. It takes discipline to practice spirituality and inner peace. Without this fire within, we cannot make a connection to what lies beyond the cycle of birth, reproduction, decay, and death. We must love our inner beings much more than we love our capricious minds.
  
  

• Joy. Enlightened ones are happy because they are not the victims of their chattering monkey minds. Enlightened beings trust that Universal Harmony is the Law of the Universe and therefore do not life fretful lives. This is deep, inner joy—not just the superficial happiness that comes when our cravings are satisfied. That happiness goes away when we are deprived of its objects. Joy stays as the foundation of their being.
  
  

• Relaxation or tranquility of both body and mind. We can feel when someone is in inner turmoil. They show it in countless ways, from nervous tics to having meltdowns and tantrums. The enlightened ones accept What Is and don’t fight it. They solve problems naturally, without feeling they need to control everything and everyone around them.
  
  

• Concentration—a calm, one-pointed state of mind, that fits into the above “relaxation and tranquility.” This is usually done through meditation. Yet we don’t need to sit endlessly in the lotus position to attain this one-pointedness. It happen all day long as we stay mindful in our tasks and activities, or just sit and contemplate the glory of What Is.
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• Equanimity: In Buddhism it means to accept things as they are without craving or aversion. We can spend our whole lives reacting to things. I hate this. I love this. All based on our conditioning, experiences, and opinions. Cravings drive us into a endless path of dissatisfaction. For once the craving is satisfied, another one comes up. Or we just want more and more of what we think will make us happy. Aversions cause us to live a life of disgust with others and moral self-righteousness.

As for people disappearing after they have become enlightened, even the Buddha hung around in the flesh after he attained enlightenment. Disappearing is a romantic and fairy tale view of enlightenment. When people asked the Buddha, “What do we do after we become enlightened?” He asked, “What are you doing now?” They said, “We’re chopping wood and carrying water.” Buddha said, “Chop wood and carry water!”

Enlightenment isn’t a state of fireworks, peak experiences, and mind-blowing sensations. It is a simple approach to daily life that many people may not even be able to notice. But as we are chopping wood and carrying water or going about our daily tasks, we hold them in a different state of consciousness—as something precious, miraculous, and in the NOW.