FWIW both instances I've read about being locked out by Comfort Access (including the one described by the OP) involved the key being in a purse placed inside the vehicle and when the door was closed the X5 was locked with the key inside. AND in both cases, the door being unlocked and locked was NOT the driver's door.

Note: Without Comfort Access the only way you can unlock a passenger door is to have previously (or simultaneously) unlocked the driver door.

Funf Dreisig