Hi,
When you say "disapearing" you mean in t-code CS03 when you display the BOM contect it is not there? even if you diplay w/o giving dates?
You can check also tables - STPO will contain all BOM items (some of them might not be visible in transactions). To get STPO records you need to know BOM number - it is assigned to material master of main mtrl (the one that has BOM). The field is called STLNR - check it and diplay all component records from STPO.
I know that if you do operation like this - add line with DCN 1 and remove same with DCN 2 it is visible in CS03 unless the date of DCN 2 has been moved later before DCN 1. If this is done, item "disapears" from BOM, but still can be found in tables.
Regards,
Tomel