it's possible that its a plastic flange that simply broke either from the rocking or snapped when you tried to tighten the bolt.
This is what happened, a piece of the PVC flange broke off where the bolt is seated. I fixed it with a steel ring that sits over the PVC.
Oatey Stainless Steel Replacement Flange Ring ($6)
I replaced the screws that were securing the flange with 2" coated deck screws.
For the steal, I tried a Saniseal but I wasn't very impressed. There is an inner ring to the seal that is supposed to fit around the porcelin the protrudes from the bottom of the bowl. Then only way I could get this on was to put the seal on the toilet and then lower it onto the bolts. The seal wouldn't stay in place and I could never convince myself that everything was lined up correctly. They should include some heavy double sided tape with this so you can secure the seal in position on the toilet.
I ended up using one of these,
NEXT by Danco Perfect Seal Toilet Wax Ring with Bolts ($10)
This is a kind of hybrid product with a wax ring and a silicone seal. It has much longer bolts than the saniseal product if that matters. I would have just used a reinforced wax seal, but there were allot of sizes there and I didn't have any way to know which size I needed. I didn't see anything stamped on the old one, which would have been nice.
I also got my own stainless steel washers that are larger than those provided. I got the kind that are larger but have a small hole in the center. The slots in the porcelain on my toilet are wide and the washers that were on there were not wide enough to cover all of the slot so they didn't sit very flat. I also got some neoprene washers to go under the steel ones so I could tighten them up well against the porcelain.
Overall, the toilet is sitting flat and not rocking anymore. I am still not entirely sure about the bolt in the broken area of the flange but it seems alright for now.
Overall I am disappointed with this bathroom. It is 6 years old and was built with high quality, expensive fixtures bought at a well regarded regional plumbing supply company. Everyting is Symmons or Toto. So far I have replaced the spindle and seat on the shower blender, the drain in the pedestal sink, the entire inside of the toilet tank including the feeder hose, and now have repaired the toilet flange and replaced the wax seal. Also, the new toilet shutoff valve doesn't work and I still need to do that. Before the remodel, the bathroom that was there was installed in the 1950s and didn't require any repairs that I can remember in the 30 years I lived here before the remodel. Everything still worked but the floor needed attention and it was looking old and tired.
...but everything still worked
It seems like you need to remodel every 5 years now if you want everything to work.
Thanks for the help.
LMHmedchem