People in comas don't act like they sleep. When they finally come to very few say they ever had sleep or dreams. Comas aren't like long naps they are like moments where your brain stops working except for blood flow and your brain stem keeping you alive. When those people come to, they may feel extremely weak and confused and likely won't be concerned if they may have dreamt or not. Most humans forget their dreams within 5 minutes of waking up.