"What would the IAEA have done with the complaint?" - Ben It would have requested that it be permitted under the terms of the NPT to inspect the site. If Syria refused, that would be equivalent to a confession. If Syria allowed an inspection then competent technicians would have visited the site, inspected it, and taken samples which would have determined whether or not the site was in fact a nuclear facility or not. Such an inspection, also, if not proving it was a nuclear facility, would have conclusively proven it was not. Which might be why no information was filed with the IAEA.
from the article: PM makes first public hint at alleged IAF operation in Syria