The list only shows addresses that have found a share recently enough to be owed a payment in the next block. If you go for a long time without finding a share (as will happen with a low hashrate), you will not be on the list.
Thank You!
I've set up my P2Pool node at http://cryptominer.org/bitcoin/ to be more friendly to low hash-rate miners like yourself by counting pseudo-shares with a much lower difficulty than p2pool itself accepts. If you decide to use it, you will get a smaller, more regular payment. The amount should average out over the long term but will be more consistant on a day-to-day basis.