Detachable trailer coupling torn off

Hello, who has experienced this before, or who knows such a case???? Yesterday 05.06.2004 we picked up our niegel nagel new caravan about 10 meters in MG with a Volvo V 70 with removable trailer coupling. Super max trailer weight 1800 kg. Through MG right…left…high…down…braking…starting…… everything ok!!! After 50 kilometers on the highway (tempomat inside) look into the mirror and a set of my husband “Now he’s gone”. Shock, a look backwards and there he rolls. M Seeling alone towards the guardrail!!! At the guardrail he came to stand after a few meters. a starter of 20,000,– € 4 hours old 50 km driven, a damage of approx. 10,000,– €. Great!!! Does anyone know about this??? Can someone tell us or help us how the case law looks??? The safety rope was attached to the clutch, but the hook was attached to the trailer (the entire removable trailer coupling, enticed, safety bar closed).