Good point. I guess Edmund's contactsmight help here
I believe judging from the published stuff out there that there is a general hype that apparently worked on the Argentines and that is the VIFFing/AIM-9L threat. Now I don't know how accurate such statements are and I think it maybe the case of people confusing hindsight with reality; and the reality might be that the Argentines may not indeed have known of the existence of the Lima version. Having said that I'm sure it won't be difficult or won't take long to find out...in addition at least one engagement might rouse suspicion and that is the 1 May Thomas head on merge with the two Mirages. He did not acquire them head-on with his all aspect missile and I believe Ward in his book (speculates?) that they were not in reheat (afterburner) or that they had throttled way back? So it is likely that they (Argentinians) were very aware of the Lima threat. But it might just be that they were conserving on fuel and entered the pre-merge without having it on. In any case it would be a good pre-merge practice to reduce one's IR signature for potential missile locks (which may not necessarily come from the bogey you see
head-on but rather from the unseen one who might be working his way
around you as it happened in this case with Flt Lt Barton hooking around the back of them and taking the rear shot).