The first couple times, I thought maybe it was user error or a fluke or something.  But this just happened to me again, so three files in the last month, and maybe five in the last year.

I'll open a part, and it will have no features in it.  The feature tree is there, default planes, origin, annotations etc, that part of the tree all looks normal.  But there are no features, as if I started with a blank part file.

Doing a search on here, I don't see anyone else mentioning it, so maybe I'm just lucky?  Anyone else ever hear of this?

Ok, before clicking "post message", I tried something.

It turns out that it happens when I open the part from the assembly.  If I close the assembly, then open the part by itself, the part is normal.  But if I open the assembly it's in then right click on the part and click open part, it comes up with no features.  But If I close the assembly again and just open the part, it's fine again.  This is at least annoying, and I'm a bit concerned that someday it might really bite me.