It is possible that the worms could have escaped, but the more likely issue is the worms you found. There are many different kinds of worms, but the ones best suited for composting are the Red Wigglers and African Night Crawlers. It is possible that the bait worms are African Night Crawlers, which I know are great for composting various types of manure. However, I bought a box of baby red wigglers with my Can-O-Worms about 2 years ago and the upper containers are filled.
Since I am responding to an old post, I am curious how the bait worms performed over the past year.