After about half an hour in the middle of the road (with the guard helpfully offering me his chair to sit on for want of any other help he could provide), another and clearly more clued in guard appeared who pointed out that since the hostel reception was open till 1 PM on Sundays, I should just go ahead to the CERN hostel, except for the small problem of now having to drag my bags along with me for something like half a kilometer. Fortunately a kind soul (who turned out to be Indian and knew me, though I, for the life of me couldn't recognise him) gave me a ride just as I was starting the trudge. And of course, the key was indeed at the reception, and the story had a happy ending and I didn't have to spend the day sitting on a sidewalk.
A small incident really but the number of missteps is quite amazing. The secretary omitted to tell me that if I arrived by 1PM I could go to the reception directly but instead asked me to pick up the key from the security gate (despite knowing my exact arrival time). The guard, even more surprisingly was totally clueless -- all the more astonishing when you consider the hundreds of visitors CERN gets all year round. You would think that visitor handling would move like clockwork (its Switzerland after all!) in a place like this. I can't help feeling that, whatever be their shortcomings, all guest houses in India are geared to handle visitor arrivals at all possible hours. This is, after all, not rocket science, and CERN handles far more difficult problems!
As one wag pointed out, that's because Geneva is really not Switzerland, it's more a French city :(