Step one bare off downwind and unhook, then load and pop in to your chosen trick. land downwind and hook back in. then you can spin your bar out.
Warning- spinning your bar out unhooked is a bad idea!
just joking, I have had the same problem lost my kite 3 times in 2 days lucky for me timmy and Vicy managed to get them before they got damaged. What really sucked is that it was perfect for unhooking and learning new tricks and spent most of the time on the beach. Most of the time i run sui leash so expect that when i let go the kite will still be there sux when its not. So my quick fix was to get the slingshot hammerhead spreader bar to replace the mystic one the hole system seems to work better, and if you double check it before unhooking your kite will be there no matter what, no qr on the leash and a good rope around the back. Plus i like the hook better than the mystic one, gives me more confidence to not run the chicken dik.
so far so good, but hopefully wont have to drop the bar on to the leash to often, Good luck