I would much appreciate any advises on the below.....

I am on a FTC currently (mat. cover) and my role is assisting to HR advisors who particularly deal with ER cases. It is an admin role. 

In my previous job I was a HR coordinator with more broad duties, still admin role but covering all areas in terms of HR (from onboarding till termination, including promotions, maternity, expenses, benefits, pension, flexible working, sponsorship, HR software, etc.   .... a lot of staff....).

Last week within my current company was advertised an internal role of a HR assistant to work closely with HRBP and regional HR manager. 70% of duties were admin ones, so I've applied, but I wasn't successful, because as they argument it - I even didn't understand the role duties...which is so weird to be honest, but I didn't argue as most probably the role was intentionally created for a specific person (not sure, so just assume). Next day I've been given a feedback and told that I have a great potential and they will see what with they can engage me to get more experience and understanding about the HR assistant role and HRBP role. I said I am more than happy.

To make it more clear if to compare two jobs, then in a previous one I was busy on 100%...and in my current one - only I would say on 10%. I didn't expect it like that when I accepted it and I feel I am loosing my time. Just for clarity - all HR department has been made redundant in my previous job due to relocating it to an EU country. 

Yesterday night I suddenly saw an advert for a HR administrator for the Manager who interviewed me last week. I was surprised and even shocked. Why would they advertise it and not offer it to me, or at least discuss it with me (taking into account they said I have a great potential)? Why would an employer bring someone into the business from outside and pay them when people who already work for them are not fully involved in the job and are asking for it and are considered to have " a great potential". 

I am so dissapointed and upset with this prestigious and famous employer and with how they treat employees. 

Yes, I agree I am a foreigner with may be not that 100% fluent English, I don't may be have enough experience as all my roles were more admin ones, but I have my CIPD 5 done couple of years ago and I am finishing my MSc in HRM this year, but I want to learn and progress and use all my knowledge to benefit the business. And is very  frustrating and embarrassing when you understand that no one cares and that  all words are mere.