As far as I can tell this is not a scam (though the owner MAY want to choose a different name for the pool, the old Powermining was definitely a scam and shut down by the SEC). Mining in a small pool has a different risk/reward than a larger pool, you should always research stats and pool size before joining one. From what I can tell, you were paid fairly; if you think otherwise perhaps start a discussion in the powermining thread, you'll likely get a much quicker response.