Hi Looking,
There definitely is a way to know if that primary offer has fallen through. When you submit your back-up offer, have your agent submit the CAR form P.A.A. This is an addendum to the purchase agreement. There is a space on the second page that contractually indicates that you are back up offer # _______(fill in the blank). We use this when we make offers on properties and also when we accept offers on short sales as so many fall out. It helps everyone to know exactly where they are.
Good luck. I have purchased both of my homes by being the back-up offer! So many escrows fall out these days - it is a smart strategy.

Hi Looking,

I have found that is not always the case. I would recommend that you have your agent stay in close contact with the listing agent for this property. Also you should continue to look for another home and consider putting in a second offer on any other homes that you may like. Your agent can explain this process further to you. This will give you a back-up. This is especially true if you're looking in the short sale or bank owned markets. Good luck!

Matt