can you reinsert it?
hi g.g. just to clear up what i meant. Flanges can be made of many different materials, Brass, ABS, etc, and even partly this or that, and so i thought you had it right in front of you and you could tell us more. But that may be irrelevant now. Also, it may not even be broken.
I read the above, and I thought it made sense that the bolt had slipped out of its slot / groove in the flange. Have you been able to confirm this or see this in any way? You might try loosening the bolt + nut a bit (unscrewing the two a half-turn or so), and then inserting that end piece (the oneinside the toilet base back again into its slot in the flange, although it is a 50%-50% guess whether or not you will have the unobstructed open space to do this and it is true that you cannot even see it. If you can get the bolt head back into its groove, and then tighten it a touch, you'll have achieved your initial goal.
David