Can someone still have a heart attack after the cardiologist saying that every test looks normal and theres no evidence of heart disease?

Possibly: Though unlikely. If your cardiologist says that your vessels are clean, you should believe them.

Absolutely: No test detects everything; one may have a genetic predisposition, or one may use drugs that can cause a heart attack. Need more info if you want a more personalized opinion.

Why not ?: Tests and evidence show what is happening at that instant and what has happened in the past.. They cannot predict the future.