Originally Posted by drowling23

Thanks for the responses, everyone, but I've been an idiot, assumed the tires were tubeless because they were stuck shut to the rims. In fact I figure they might have been stuck deliberately, or it could have been an effect of inner pressure against the rim. At any case, I got them unstuck (took a lot of force!) and hooray, there was a tube down there after all.

You live and learn. Also learned that Rohloff is really easy to disconnect.