Contingent with a short sale means the bank is working with an offer. It doesn't mean it's in escrow, and buyers walk all the time during this period, leaving the short sale seller needing an offer sometimes. They may have back-up offers, but those buyers are still out submitting offers on other properties too, and may not be there if the current buyer walks. This is a good time to submit a back-up if they don't have a ton of them already. Sometimes though, short sale sellers don't want to show anymore, because they don't want more people through their house if they already have an offer. It's a sort of false sense of security, but they usually aren't in a happy frame of mind. If you REALLY like a house in Contingent status, try to get a showing, or you can always submit a back-up offer contingent on you seeing the property in person.
Cory La Scala, REALTOR