The "wives tale" is just that...a tale...it doesn't work.
Do we know if the vehicle has power? If so, and inserting the key manually into the driver's door lock cylinder and then turning the key counter clockwise PAST the electronic actuation of the key (approx 90°) doesn't unlock the door...what happens if you hold the key until the "convenience open" feature starts to roll the windows down? (again, do we know if the car's battery is dead or not?)
If there's power, try the convenience open feature, once the windows are down you should be able to reach in and unlock the doors (if the doors weren't double-locked).
To double-lock the vehicle requires it to be locked with the key (either remotely or manually). If the car was locked up by going thru any of the passenger's doors and manually locking it...then the vehicle is in single lock mode and a double pull of the door handles is all that's required.
BMW changed the operation of central locking around the 2000 model year...and now, if the vehicle is double-locked...you can now open the doors from the inside...but you have to follow a procedure first:
- press the central lock/unlock button on the center console first, then
- pull one of the door handles twice, and it should open.
Manual UNLOCK procedure (when there's electrical failure...and other remote key doesn't work):
Even though the door handle is different on the e38/e39/e46...the lock cylinder positions are the same:
