Think that you have enough rows for that index?
Maybe not. Recently I was working on some demo scripts for a future presentation which included things to look for in an execution plan. Namely, RID/Key look ups. Naturally, I had built out a table, applied a clustered and non-clustered index, and started to run my queries. Based on my queries, I fully expected a nice look up to happen, which would prove that my scripts were working as I expected.