After flipping the switches all you want, and assuming you can go downstairs to look at the bulb once and only once, how can you find out which switch is connected to the bulb?
Don't peek ....
Here's one solution. Pick any of the three switches and turn it on for 5 minutes. Then turn it off and turn on the second switch and go downstairs. If the light is on then you know it is the swith you just turned on. If the light is off feel the bulb, if it is warm then it is the first switch you chose. If the bulb is cold then it is the switch you didn't touch.
How did you do?