We can observe Pillars of Creation with 7000 years delay, but it is destroyed only 6000 years ago. How do we know that? How the information about explosion reached the Earth before light do?
Much of the evidence for the destruction of the Pillars of creation lies in observations of dust clouds in the region (Flagey et al. (2009)). The morphology and structure of a cloud in the dust are suggestive of a shock wave, which seems to be indicative of a recent supernova. The shock waves from supernovae do often interact with both the interstellar medium and local gas clouds. The original observations supporting this hypothesis were made by the Spitzer Space Telescope.
It should be noted that the SST uses infrared light, and as the dust wasn't seen in the visible portion of the spectrum, we wouldn't necessarily have realized from the Hubble photos that there were any effects from a hypothetical supernova.
Some dissenters believed that something completely different is responsible for the behavior of the dust - possibly the winds of massive stars. Now, more recent x-ray observations (see e.g. Guarcello et al. (2012)) have failed to see either the x-ray spectra expected of O-type stars or the x-ray emission that would be indicative of a supernova, leading some to conclude that the Pillars of Creation have not yet been destroyed.