This happened to us a number of times. An old cliche but these things happen for a reason and indeed properties do appear back on the market. We sold eventually and have just had an offer accepted on a property that we would never have considered before.
This happened to us in the autumn. Fast forward to now and we're actually sitting in the house which went under offer and was in the process of being bought by another couple. Keep an eye on it. Ring the agent and let them know if any thing falls through, ring you immediately. We got the call immediately after the buyers pulled out. Five weeks later, we'd exchanged!