Things usually don't happen from sitting, they happen when the engine stops, and then they just wait to jump out and bite you. Cam gear nuts are supposed to have a locking plate that bolts on to the gear and fits over the nut, you can see them in this picture. These pulleys don't have accessory drives bolted on to them.
That this point I would drop the oil and stick a magnet on a stick thingy in to fish around and see if I could find a few bits of whatever the gears ate. Then I would probably drop the pan and fish out the parts to see if any of them were gear teeth looking bits. Then I would probably take the back cover off to see how many gear teeth I lost.
Note to self - never try to spin a locked up engine, it's usually locked up for a good reason...