My own theory is that the wire, probably picked up on the tyre, derailed the chain, which then got caught between sprocket and hub, causing the circlip to jump off.
I've never looked very hard at the gap between Rohloff hub and sprocket - if my theory is correct there would have been substantial leverage in this gap, which might explain the oil leak - maybe some damage to the seal.
But perhaps less overall damage than would have happened with the old system, where the steel screw-on sprocket would in all probability have stayed on, and the chain plus bit of wire might then have chewed up the alloy hub shell.
I think this kind of thing is a rare occurrence on a hub-gear bike. Had it happen to me once on a derailleur bike, wire got caught in the derailleur, derailleur twisted into spokes and was ripped apart, causing slight damage to spokes. And seen it happen once to a rider in the same group as me.
I've had one chain derailing problem on a hub-gear bike in about 4 decades of hub-gear use - a very slack and very well worn chain jumped off the sprocket and into the gap between sprocket and dropout. Not sure whether I had picked up any debris that might have triggered the derailment. I remember it was hard getting the chain back on, but I managed it without removing the wheel, so the chain was very slack indeed.
Over the same time period I've had lots of chain derailing problems with derailleur bikes, with overshoots into the spokes or into the gap between small sprocket and dropout, and on bikes without front derailleurs the chain coming off chainring when shifting the rear derailleur.
If compatible with the chainring/sprocket combination, a Chainglider should be effective on a hub gear bike to prevent derailments caused by wire or other debris, but it might make a spontaneous derailment due to too much chain slack more likely, as it hides the chain from view.
