Steps to reproduce:
Zooming out of a small object it vanishes
Expected result: should show still when zooming out
Actual result: see video here: Dropbox Capture
Does your object have LODs
Open Debug model Lods
You will see that, mostly because you have only a single LOD , because of enforced Lod system , when zooming away your object is too much complex
Add less detailed LODs and it will stay in place
Monitor closely the debug model Lods/statistics profiler