Power supply: mysteriously working again

The day after claiming that my PowerBook's power supply was no longer charging the battery, I moved rooms, plugged it in again for a last check before taking it in for repairs, and, of course, it worked. And it's still working. So, although I certainly may have a faulty adapter or cable (or, worse, PowerBook), there's not a lot I can do about it now, as I'm super-reluctant to take it into the store when I can't replicate the problem. I may as well drop it off and say, "Please charge me for several hours of labour, and return the machine unchanged" since that is what would happen.

PowerBook