It's not attached at all. There is a raised circular area surrounding the gas burners - just a couple of mm high. Around the circumference of this raised area are four small indentations (about 5mm in, max) which more or less locate the four feet of the pan stand. It's barely held in place by anything at all. Less so than with other hobs I've had/seen.
I don't know how it happened, but I was manipulating a large frying pan and somehow it dragged the pan stand with it some distance - it had to in order to get it fall off and onto the floor. Most bizarre, it was. Baffling. It just seemed to take off and fly.
Anyway, it's very easy to push the pan stands out of location.
Michael