First off, Welcome back! Second, if your looking for a faction, go to the forums list, scroll down to where the realms are listed, choose the realm of your choice, and then there you can find recruitment threads from different factions. There you will be able to apply to join someone’s faction!
Do you have proof of you receiving the money and then losing it? If you can not prove that you lost 500k then there is nothing staff can do unless it is a known bug. Also, did you possibly spend it on accident?
First off, Welcome back! Second, if you are looking to join a faction, go back to the forums list page, scroll down to the realm names, choose the realm you like and then click recruitment! From there you will see a list of the factions that are recruiting. See ya around :D