If their agreement is mini-Roman, South is allowed - required, in fact - to remember that that *is* their agreement for the purposes of Alerting, but not for the purposes of her own auction.
Things kind of break down a bit with insufficient bids, especially as in the ACBL, *NO MEANING* can be assigned to an insufficient bid or calls and decisions afterward.
So:
- After 2♦!-p-1♠-2♥: I think that this "usual hand" will pass happy to have got out intact. Note that had North bid 2♠, correctly, South would have to Alert this as "pass or correct", but bid as if partner had made a (presumably forcing - what does the card say about new suits over the weak 2 bids they do play?) call.
- After ...p (? or no call)-no call-2♠-p: I don't think any other call is a reasonable LA (partner would double with a huge hand, wouldn't he?) but it's worth checking.
- After ...p-, why West thought that the auction was over I don't know, as only two passes had been made after the last call and the TD was there (the TD *was* still there, right?)
Unless South is known to forget mini-Roman, E-W got the correct agreement and the correct explanations (if I as South was asked about 1
♠, I would say "2
♠ would have been P/C; I don't know about 1
♠"). I would ask peers, giving North's explanation of 2
♦ as "weak 2 in diamonds" (with whatever caveats as to style I can find out - is this a bad weak 2 or "about expected" for this partnership (were it some other suit, obviously)?) and see if anyone takes a call after 2
♠-p.
Specifically, E/W are not entitled to the knowledge that S forgot and misbid (again, unless North has experience of this before). E/W are not entitled to "what North's bids would have meant if they were playing what South thought they were playing when she opened", either - well, they are, yes, but only in context of "if you had opened 2
♥ weak, what would <> have meant?" and certainly not as what partner has in this auction. Yes, that sometimes means that those who misbid get the better of the result (in the context of weak calls, it's more likely; more yet when both the "natural" and the "systemic conventional" meaning is weak (See Ghestem, or Suction as it's usually played in my area (the next suit up, or the other two, or the suit bid, because bidder forgot again)). This breeds the concept of "systemic germs" and "CD", but it doesn't give them any context in Law.)
If, however, South is not convinced that North has given the right explanation of their agreement - if she thinks they "switched to weak 2
♦ last week and haven't updated the card" or the like - then all that gets thrown out the window, and South must explain North's bids (as she can, at least) in the context of a natural 2
♦. But when there is no doubt that North is right, then to explain something else is MI.
[Edit to add: I do not believe that AVE is a legal score, unless the TD erred (by, for instance, not remaining at the table to ensure everyone knows what's going on and that even with all of this, three passes are required to end the auction). Even then, I would expect an Assigned Adjusted Score, not an Artificial one. If South is determined to have no LA to passing either 2
♥ or 2
♠, and there is no history that would imply that N had prior experience about these forgets, then E/W have no case (but my sympathy. Not much sympathy, as both East and West could have done saner things after the irregularities, but sympathy nonetheless). If the TD determines there is another LA that is less successful for South, then the result of South making that call should be assigned. "Checking the scores" should be actively discouraged, especially in a case like this where not everyone, even were they to play a weak 2
♦, would open. After pass, it's much easier to get to 4
♥, I am sure].
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)