First, what is the booking site? Others here may have had experience with that site and may be able to offer valuable advice. But, they can't do that without knowing its name. In addition, others who might be considering booking, ought to know so they can avoid it.
Second, initiate a chargeback dispute. Make the description short and sweet. The back-and-forth in your OP is not relevant to the simple fact that the owner/agent agreed to meet you and did not show up for 2-1/2 hours, so the contracted service was not delivered. You have 60 days (although some card issuers may allow more).
Not to berate you, but for the benefit of others, when there is a clear service failure, e.g., nobody there to let you in and no code for the lock, send a text to the owner and an email/text to the booking site immediately. If you do not hear back, initiate the chargeback immediately. The passage of time does not help.