A gap down? If it was a gap down I am pretty sure it has already been filled.
I am assuming you mean a gap up, but May 2009? I am as interested in watching gaps as the next guy, but I think surely there has to be a point where a gap becomes irrelevant.
I am pretty sure that Flight Centre's plunge to 3.39 in March 2009 had everything to do with panic on global markets, and nothing to do with a gap up from 6.22 in April 1999.