I suspect it was less than 10knots to have this problem.
Try learning to down loop the kite
If it has flown forward in the window and not making any more progress where you want it to go throw in a quick downloop.
Once it is flying back in the opposite direction fly it back up and sheet out to help it get there quicker

This gets it flying again so you can regain control.
If you take to long to make the decision it will just crash into the water, you have to keep it flying, even if its not quite what you want to do at least it keeps it in the air
This is a good technique for light winds as when you tack and dive the kite down it sometimes wont come back up, so the down loop gives it some speed, gets you on the plane and off you go, after some practice