I'm a big advocate to making a starter anyway, especially when using liquid yeast. If you make a starter, there just isn't the uncertainty that you have when using liquid yeast from the package, even if you use a smack pack.
Also, when I started using starters for my batches I think it was the single best improvement to the overall quality of the beer I produced. Just something to think about.
Back to your question though, was the liquid inside frozen or was there just ice on the outside of the package?