I am trying to understand what happened for you, @Sean541 but I don't know what time frames you are dealing with in terms of your booking. Also did you book another place while waiting for some message from the host of the original booking? If you requested to book the first place, it means to me that Instant Book was not available for you. Therefore at the time of the request, Air BNB qualified you as a guest by running your payment. The host has 24 hours to respond in accept or decline. Now, here is what is not clear for me, it appears while waiting you opted to actually book another place that was better suited due to the self check in, right? When a guest does that, it is my understanding that the previous request then appears in the host messages as no longer possible. Therefore it keeps the same guest from booking two places at the same time. Now, of course Air BNB is the best provider of the information you want so I suggest you call Air BNB. Here is a guide for contacting Air BNB.
https://community.withairbnb.com/t5/Help/Contact-Airbnb-A-Community-Help-Guide/m-p/16165#M728