You got an extra ")" in your code. It should be this way:
oListItem.set_item('Pieces Unaccompanied Hold Baggage(Rush)', "value");
But, in oListItem.set_item() method, the first parameter shoult be the INTERNAL NAME of the field. You will find the internal name in the URL when you open the field (column) settings. So it should be
Possible Work around: Check "Show all items without folders" for your views.
Possible Issue: For whatever reason, the item is being stored with-in the Item folder inside the list. It is a system folder and not visible in views.
I had this same issue with one of my lists with an infopath form. Every now and then an item would be missing, but could be ...
Change your header attribute "XML-RequestDigest" to "X-RequestDigest".