When you referee, with ARs, the bottom line fact is, as referee, you have the ultimate responsibility. Its widely accept though, granted, to use the EXCUSE, because afterall that it what it is, that, my AR flagged/never flagged so I went with it. Usually, that's seen as undestandable.
However, bear in min, each and every time that flag goes up for offside, in basic terms, its a signal from your AR that he believes someone should be penalised for being in an offside position. Its nothing more, nothing less. Now, 99 times out of 100 on auto pilot, as referee, we accept our colleagues judgement, Its vital though to be able to separate the two roles played here, one is in control, and one is, assisting the referee with that control. You can easy go through a whole season of having little dispute with ARs. So, nobody is saying, go out every game with a view to over ruling, however, its not as black and white as too many officials view things, oh right, flag is up must be offside.
And, in even rarer cases it works in reverse. If you are an alert, aware, tuned in referee, you are generally conscious of your ARs position. Friend, (not picking on him, but as he was the ref in question) is surely looking to that action area anyway. He has to simply see the AR is not ideally placed and think ahead, right, my AR wont be able to call this, so, can I help......
Far too many refs go out there with a mental block that, there is no flag, so it cant be offside. And, you can limp on by vast majority of times like this, and as stated at the start, you can always fall back on (blame) your colleague by saying, well, he never flagged so that's that
That's weak refereeing.
As someone else pointed out, we dont know what if anything was said on comms, am sure now with hindsight, Friend would have went "thats offside, am giving it, flag NOW ". That to me would have been fantastic officiating, ref doing what he should, taking absolute control, and AR, albeit slightly delayed, flagging, nobody will fault him for a late flag, nobody really knows the ref shouted on him to flag, and we avert the scoring of a goal which should not have happened.
of course this is Utopia, but, if this forum is about learning off each other, and thinking, right, how could have that been done better, that is my input here, a referee who is not afraid to turn in a huge call when needed, and sharp enough to smooth over a bumpy situation with the correct call being made as a result.
I like to think to a man we would applaud Friend had he made the call. As it is, he never. So for that he deserves appropriate share of blame for the incorrect call
Do not be fooled into thinking leave offside simply to ARs. or do if you wish, then find yourself in this situation