Why does HR disappear after constant communication with a potential employee?

Hopefully somebody from HR can help to answer this. But why do the people communication with employees disappear as time progresses? This is the second time that I’ve had constant communication with HR, just for them to vanish.

Are they busy? Or they just don’t care to finish something they started? Either way I find it rude but I would love to know.

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official