Just wondering ... did you or someone in your party spend (not necessarily lose) a lot of money in the hotel casino in Vegas, on this or a previous trip? That's one reason they might have comped you the room.

Wouldn't explain Baltimore, though.

Either way, I'd take the freebie over points worth maybe 2% of that. There's no ethical issue. You weren't trying to get away with anything. They know you were there, they have your credit card, they opted not to bill you. Be happy.

If a bill shows up on your credit card later, demand the miles!