[Ian McColgin]

Since I've never seen an anchor deliberatly hooked on a bobstay, I wonder if there's a terminology issue. Up here, the bobstay is the one that goes from a chainplate on the stem near the waterline up to the end of the bow sprit. Whisker stays or sprit shrouds go from some nice place on the gunnel abaft the stem out to the end of the bow sprit. We do see anchors slung from the latter now and then.

Maybe a picture or a more coherant description will help me understand whatever you are seeing so much of down there, that's so very uncommon up here.

Edited to add - On rereading your post and seeing chain mentioned, I take it you mean a real bobstay. I'm deeply prejudiced against chain bobstays but that aside, I can't even imagine how one would hang an anchor on the bobstay or why it would stay in place.