My situation appears to be different to yours, so this is just what I do.
I am guessing your shackle just parted company and the weight of the chain kept you quiet until breeze increased to 10kn. Things can happen no matter how well you prepare.
I use galvanised chain and anchor and tested galv shackle to join chain to anchor. Shackle is moused. I usually use a long snubber line for stretch and a big loop of chain between snubber and boat. I have No.2 anchor on its own chain ready to go no matter what.
In quiet conditions you usually need not use more than 4:1. (Did you really have 12:1 out in <10kn of breeze?) Do you 'set' the anchor or just drop it? I use a trip line if I am worried about it or cannot dive down. I would oversize the anchor and chain, but not too much.
If I am worried about dragging - I mark the position on the GPS where the anchor was dropped. If I have 60' of chain out, then I can move no more than 120' - [usually only the 60']. Any more and I am dragging. This hasn't happened yet with my combo, but peace of mind is worth a lot if worried and tired.
Last edited by St Anna; 08-10-2009 at 11:06 PM.