This would never be possible in Marketo because it's the browser that fails to redirect from the tracking server to your site. Marketo's server never knows about this.*
There 's a chance that if your site was accessible, but returning 404 or 500 errors — it isn't clear whether you mean "down" as in "completely unreachable" — your IT team has web server logs that could be used to reproduce the referrer, which if you worked painstakingly, could be tracked by to an individual email. (Boy, would this not be fun, but depends on the level of emergency.)
*Yes, a different purpose-built server could potentially know if a destination server was slow
based on the time taken to disconnect, but I'm only writing this on the
0.00001% chance that someone pedantic comes across this post.