I have Radz brand vario 20-30 harness lines. They have a small white plastic ball on the buckle for quick adjustment. Two days ago I was out, and blew a gybe - and ended up under the sail - when I went to release the hook I was locked in by something - didnt know what - just that I couldnt get out! Luckily I was just able to get my head just out of water to get breath, and then undid my buckle on my harness. Turns out that the adjustment ball had inadvertently fallen in the gap between the wires of hook, and under my body tension, locked me in there. For a moment there I thought I was in a drown scenario! Have since cut them off

It can be really scary being caught under your sail and unable to unhook.
Glad you're OK.

The same can and has happened with other lines. Eg. some lines have a finger hold loop instead of the ball, the loop can catch the hook os slip through the hooh like yours did. It is very scary and disorienting when it happens.