I used either a Petzl 8mm Accessory Cord, or Teufelberger 8mm Reep Schnur. The Reep is more supple and easier to stuff into the ditty bag.So the carabiner that attaches your spliced eye to the 8mm cord is essentially a backup to the hitch hiker knot as well. I like it. Simple.
Are you using something like this for retrieval? http://www.treestuff.com/store/catalog.asp?category_id=259&item=1472
Stuff is cheap but I have never used it.