Generally nothing happens just because the summoner has been knocked out (or gone to sleep). Indeed, now that in 6we spirits last for one sunup AND sundown (rather than the first of the two to occur...) it's pretty much assured that spirit services have to persist through the mage being asleep. That in turn gives support for services persisting through the stun track being filled up. Furthermore, "holding on" to spirit services owed isn't said to require concentration, contrasted against the example of sustaining spells (which cannot persist through being asleep/unconscious).
Mind you that in prior editions, there HAVE been suggestions that poorly treated spirits might try to slip loose while a mage was on death's door, but it's varied as to what kinds of spirits might attempt this: summoned, bound, ally... Of course 6we rules only treat summoned spirits thus far, but a magic expansion book is coming and who knows what will be in it. But until then, I'd say the best practice would be to presume that nothing happens with spirit services owed if the mage is knocked out. Unless, the GM decides it's more interesting in a given circumstance for a spirit to try to slip control...
