I had this happen several times. We thought it just happened to go back into the "system". We couldn't believe someone could have grabbed them that quick!!! I am a newbie, but I did see this on a thread somewhere....
- when you go to cancel a reservation for a swap , do not just cancel it.... Instead try booking a new reservation for that same time( maybe try a not as popular restaurant so you can easily find a time); you'll be prompted to either keep the old reservation or make the new one since they are conflicting. When you cancel the old one to be swapped and choose the new one apparently the old one does in fact become available. I have not tried this, but it is worth a shot!