They don't have permanent dens, and won't excavate a hole in the ground like a fox for raising their young. Look for something more like a hollow tree, tangled blowdown, or rockpile or ledge with a natural cavity, probably hidden in the thickest ravine around. Much like a feral cat with kittens, mama may move them frequently, so if you find a den today, it may well be gone tomorrow...
With the exception of when raising a litter, bobcats aren't known to bed down in the same spot each day, much less return to a den. That said, they tend to be creatures of habit, so I'd expect that it's likely one could re-use a particular cored-out oak or just as likely any of several such trees in a given patch of woods, for instance, whenever passing through that section and a big winter storm is about to hit. Which would be close enough for predator calling purposes, as soon as the storm starts to clear...
While I've never before heard a bobcat home range number floated as large as GC mentions for Missouri, I don't doubt it.
But in the coastal mountains here, their ranges tend to be MUCH smaller. I can readily think of a few areas where there are several bobcat territories overlapping within a couple of square miles, with the cats sharing prime mousing meadows via mutually avoidance, all year.
At 5K elevation in the National Forest literally at my doorstep, I've noted particular bobcats doing seasonal moves up and down of a mile or two.
Good that you found a spot where they like to sun; might be one of two dozen such spots, but chances are excellent that sooner or later a cat will return.
LionHo