The hose was actually out, with one part (inner?) of the fitting at the end of it, and the other part (outer?) still on top of the radiator. What I did was fill the reservoir with water (after the engine cool off for a while), put the two pieces together again, with hand pressure, and limped home (mostly highway) with the air on vent only. It did not come apart again but, on stop and go traffic, it may be a different story. That is why I wonder how are these two pieces held together...
This is a picture of the fitting ( I hope it works)
http://www.peachparts.com/shopforum/attachment.php?postid=152328