I called back number (02) 9977 9614 reached voice mail for a company called Clarke & Humel Property.

Caller: Real Estate Agent

Answer calls from this number (unless you are in the middle of something and can't stop). There is no downside. Most good real estate agents ring people who have attended an open house during the previous weekend. If you get a call from Clarke & Humel they are probably just following-up after you attended one of their open houses. Even if you don't want to buy the place you inspected, they will probably be interested in your opinion of the property because it helps them point out things to the vendor.