If I’m understanding your question correctly, the guest made an Inquiry, so you can go to your Airbnb Inbox on a browser (not the Airbnb app) and filter the list of messages by “Pending requests”. Then, once you get that list, you can search the resulting page for a keyword using your browser’s search function (like CTRL-F in Internet Explorer, or the “Find on this page” option in the address bar in Safari if you are on a Mac, Ipad or IPhone), searching for some word from the property title, or even the last few words that were said in the thread with this person.