From a RAW point of view: nothing happens with respect to the summoner and spirit. 6e didn't include rules/fluff this time around that spirits go free if the summoner is unconscious or asleep. And it might be a deliberate change, rather than something (Potentially among many other things) that got assumed but went unsaid for the CRB. It's absolutely a deliberate change that spirits stick around longer, and that you can have more than one at a time. So I'd be leery to say that the spirit gets to go free if the drain knocks out (or even kills) the summoner just because "that's how it used to work in previous editions."
This time around, nothing says going unconscious or dead from the drain will invalidate the result of the opposed summoning test. (a parallel to the spellcasting rules.. if you kill yourself casting a global fireball, it still goes off...) Ergo if you succeeded with X hits, then the spirit is on your hook until one sunrise and one sunset has passed... whether you issued any orders or not, and whatever your state may be until then. If you got knocked out or killed by the drain, the spirit gets about a day's vacation away from the metaplanes without having to fulfil any annoying orders... until such time you happen to recover and start ordering the Spirit around at any rate...
Edit: And yes, it does appear that this time around, technically nothing says that geeking the mage makes the spirit he sic'd on you go away.