A visitor signs themselves in by scanning a QR at the door. After that, every call, every message, every meeting is written into their journey: who made contact, when, by what means, and what they said.

The short form, the traced source, the journey in the "date · channel · logged by · note" format, the automatic move to Contacted and the journey kept on conversion all exist as shown. The people and dates are examples.
Someone sat there last Sunday. Nobody wrote down their name.
There is a book on the welcome table. The visitor does not see it, or does not dare, or the welcomer is already talking to somebody else. The result: the person who came for the first time leaves without anyone knowing they came.
Two people call the same visitor in one week; three others are never called because each assumed the other had done it. That is not an organisation problem, it is a shared-memory problem: nobody knows what has already been done.
In most tools, converting a visitor into a member erases the visitor. You then lose the only thing that had value: how this person arrived, and who walked alongside them.
These are people who came once, often without asking for anything. Better to say clearly what we do with their details.
Print the poster, put it by the door, and watch the records arrive on their own. The first call will still be yours - but you will know it was made.