Does asking about a person's life by saying, "Is this shaykh still alive?" count as envy, and will I bear a sin if this person dies afterward?

The evil eye is real, and a person may be afflicted by it from an envious or admiring soul, even if the admirer is righteous. The proof of this is the story of Sahl ibn Hunaif and 'Amir ibn Rabi'ah. The admiration that leads to the evil eye is characterized by finding something pleasing and being content with it, unlike mere astonishment, which is simply a question within oneself. What happened to the elderly sheikh after you saw him is not necessarily due to your evil eye, because what occurred on your part was mere astonishment, not admiration. Furthermore, affliction by the evil eye is direct, and it cannot be definitively asserted that what befell him was due to your gaze. Therefore, do not worry about what happened, and pray for mercy and forgiveness for the sheikh. Learn from this to invoke blessings when you admire something, by saying, "Tabarak Allah" (Blessed be Allah) or "Masha'Allah, Allahumma barik" (What Allah wills, O Allah, bless it).