I don't think this is a big deal at all. They simply have lost,...

I don't think this is a big deal at all. They simply have lost, or don't want to use whoever was doing the admin in the first place. There are so many legitimate reasons they need a new web admin. For example, they may have contracted out the initial build of the site to an agency or person whose ongoing admin prices are too high. In this case it makes sense to reduce costs by getting ongoing admin cheaper as it is an occasional thing.

How to find a new web admin? Well the first thing you would do (in my opinion) is find one by word of mouth based on contacts you have and trust. This is exactly what they have done here as most of the people who follow the MyWeps FB page are onboard with the concept and either use it or have interest in it succeeding. Its a very logical place to look for a new staff member or contractor and one of the first places I would look.

I work in IT as a web applications developer in the legal sector in Australia and I can honestly say that this is exactly what we would do over here in many cases.

Its not unusual, its normal.