I'm thinking that your pen drive shorted itself out, or something like that. It's more likely that the USB device failed, rather than the USB port. Is the pen drive made by a known manufacturer? Like Kingston, Transcend, etc.? I buy my pen drives from well-known manufacturers only.
If ever the USB port failed, you would notice it immediately. Smoke, or a quick flash, probably the PC shutting itself off are probable indicators of a port failure.