Feynman stores session transcripts as JSONL files under ~/.feynman/sessions/ (or $FEYNMAN_HOME/.feynman/sessions/). Each line is a JSON record with a type (session, message, model_change) and, for messages, message.content.
grep -ril "scaling laws" ~/.feynman/sessions/ # sessions that mention a topic
grep -il "scaling laws" -r ~/.feynman/sessions/ | xargs ls -t # newest first
To continue a session you found, run feynman --session <path> or pick it with feynman --resume.