Yes, the strut mounts do separate like that. It looks like the bearing and bearing race stayed intact even though the parts separated. The same thing happened to me, but mine exposed the bearings. I put it back together and it is all good. You should be fine doing the same, just be mindful that there is a bearing in there and if the race comes off then out come all of the little ball bearings.
I'm assuming that you stripped the new nut that came on the strut? Take the strut to the store so you can buy a new lock nut at a local hardware store. I don't know thread size, sorry, but maybe someone else does.
2012 5.0... Born on April 2011
12.70 @ 114 mph