Client showed up at wrong time and I couldn't prove her wrong — mortifying

had a client today who swore blind she had an appointment at 2pm. i had her down for 3pm. my booking process is so all over the place right now that i couldn't confidently tell her she was wrong. stood there going red in the face. not a great look for the business. is this the kind of thing that pushes you to finally get a proper system, or do others have a way of managing manual bookings that actually works reliably?