Memory is the wrong tool
People who appear to remember everyone are almost always running a system. The impressive recall is retrieval, not storage.
Once you accept that, the problem becomes tractable: capture reliably, retrieve easily, review occasionally.
Capture at the moment, not later
Anything you defer to the end of the day is competing with fatigue. Capture during the event, even if it is rough.
A scan plus one sentence takes fifteen seconds and preserves nearly everything that matters.
Review on a schedule
A weekly ten-minute pass over new contacts and due follow-ups is enough to keep a network of several hundred people genuinely warm.
Without the review, capture just produces a tidier archive of people you still never contact.