There is a minor correct for Knorx’s last comment, the two tables were host_puppet_facets and host_facets_reported_data_facets.
foreman=# DELETE FROM host_puppet_facets WHERE host_id = 47;
DELETE 1
foreman=# DELETE FROM host_facets_reported_data_facets WHERE host_id = 55;
DELETE 1
Thanks for the pointer though, this also worked for me!