That said, it's possible that an offer was already accepted by the seller before you got your offer in. Once Fannie Mae accepts an offer I have found through my own experience it is "generally" solid and no other offers are considered - even if one comes in after the fact that happens to be "better". Listing agents don't always update the MLS immediately, so it's possible a property your agent saw to be active was already under contract for all intents and purposes.
Without knowing the exact details or being a party to the transaction - it's hard to tell with any certainty exactly what happened here. I can't speak to the WI market, but in the Chicago area - good properties that are well priced by Fannie Mae go extremely quickly, sometimes in the first couple days. With the financing terms they offer through Homepath with no PMI and low down payments - these properties are becoming more and more sought after to first time buyers (especially with the recent increases in PMI for most FHA loan products).
Hope that helps!