USB Flash drive not mounting OS X
Based on the answers you've given in the comments.


The device doesn't show in Disk Utility
It doesn't show in System Information under USB
It works in other computers
Other USB sticks work in this computer
– Changing USB ports makes no difference
The device is getting warm
– It also doesn't work in another OS X system


I would suggest that there is an incompatibility between this USB stick and OS X, it could be there is some kind of damage to the sticks Firmware or a wider issue with the product that you've not been able to trace down other reports of.

Short of opening up USB Prober and understanding more about how USB communications happen, I would suggest the stick is defective and you try to get a replacement from the retailer.