First off… ALWAYS PUT THE OFFER IN WRITING!!! No matter what your agent tells you, or what the listing agent tells you, or no matter what anyone tells you…. put it in writing. If it is not in writing it is not an offer. Period and there are no fuzzy areas here.
Per Rustico’s post submit backup offers to the homes you are interested in if YOU REALLY WANT them. If you have done your due diligence and seen them, then yeah give it a shot. Note that submitting a lowball offer as a backup lends itself to a low probality of acceptance but it cannot hurt and is painless to do.
As to why none of the other properties you were interested did not pan out… well they never had offers submitted. Just make sure that you tell your agent, okay I like this property let’s write something up. Be firm, and it will happen. The agent works for you, not the other way around.