If I had no insurance and I loaned my car to a friend who had insurance and they recked it. Does his insurance have to pay for damages to the other car?

Probably.  Most auto insurance policies will also give coverage for the owner of the policy, when they are the "incidental" (not usual or regular) driver of someone else's car.  If that's the case with your friend's policy, his insurance would have to defend and pay, if he were sued and found liable for this accident.  Since he's the one who parked the car in a way that allowed it to roll into someone else's, he could be found liable.

However, if the only reason this accident happened is because your car's parking brake wasn't working properly, then your friend wasn't negligent, and his insurance won't pay.