Sounds like suicide leash to me.
Was it suicide or front line flagging leash?
And what kite? it matters (not as much though)...
Anyway, if suicide, bad idea for the conditions.
Sounds like it was suicide.
Suicide leash only works on the water, sort of.
Not so much on land.
By walking backwards with the kite dangling on the leash, you were effectively trying to fly the kite with one line, pretty much identical to if you tried to fly a kite by grabbing the CL. Can't do that with lines right, much less with crossed lines.
To control the kite, you need to control the lines. Have to get back to the bar.
In this situation, you might have succeeded if you walked downwind at the kite while going hand over hand up the leash, keeping the kite from developing power, and being careful to keep it from tumbling also -tricky situation! Then try to depower with trim and bar, leash to flagging line, try to land.... etc. Or if you are brave and the wind is light (not you case above) go hand over hand up a front line until the kite is killed.
If you got back to the bar, at least you would have some chance to fly the kite and control it.
Also, help from strangers is nice, but you can't rely on it.
I wouldn't use the suicide set-up, either, but if you do, launch with a normal flagging leash, transfer to suicide when you are in "safe" open water, and back to a flagging when you are coming in.
Any time the lines are all messed up, you have the challenge to figure out how to get all the lines except one to be slack, by any means neccessary, if possible, or you may have to ditch the kite. A good leash set up usually does it, suicide doesn't.