How did the SAS lounge compare -- better or worse?
QF does have some special lounge access rules at LHR due to the JSA with BA, giving more access than normal (per OW rules). However it does not include anytime access so the staff were kind in allowing access to the F lounge with a guest; perhaps they deserve accolades for doing that, rather than your ire for the J lounge dragons following the rules. Your real gripe is with TG for not providing their F pax with the lounge that you desire
SIN is a QF lounge (jointly with BA); not sure if the present BKK lounge is too, but the old airport lounge was also QF (which means WP access). Otherwise LAX is the other noteworthy QF lounge location where you might not expect it (labeled as AA in T4 and Oneworld in TBIT). Sadly other lounges such as HNL have been closed, no longer being a QF lounge.