David Ng said
So when you did the inspection prior to purchase did you or your representative miss this?
I think you have misuread the post. The point is that the damage was in another unit and only visible from the inside.
Under standard or “model” by-laws, the lot owner has a responsibility to ensure that common property that is part of their lot is maintained. It could be argued that the lot owner in this instance has neglected the common property and that they should be held liable for the difference between the cost of repairs because of the neglect, and the costs had the work been done at the appropriate time.
So get an estimate of the two figures, get the committee to bill them for the difference and then see what happens. This is potentially a case that would come under damage to common property and it may be worth pursuing on that basis.