I wonder if having a "leash" on the new wire could help prevent the receiver coming off as easily? While the inch-long leash I have on my Oticon Opn miniRITE RIEs drives me a bit crazy (I need the length adjusted), it does help SUPER in not only seating my power domes, but also removing my aids at day's end. Instead of yanking on the wire from aid-to-receiver-in-ear, I pull outward on the leash, and voila! Power dome plops right out of my ear canal really easy. Maybe ask about having a leash put on when you get the ear wire re-attached to the receiver? GOOD LUCK in a speedy resolution.
Things like this have convinced me to always have a backup on hand, cuz I have zero margin for error in terms of not having two working aids in my ears at all times.