Wonderful! An extra Arduino board will definitely do the trick.
Try this:
- Connect the working Pro Micro to your computer with the USB cable.
- (In the Arduino IDE) Tools > Port > select the port of the Pro Micro.
- Unplug the working Pro Micro's USB cable from your computer.
- Connect the non-working Pro Micro to your computer with the USB cable.
- Sketch > Upload
- Wait for the "Sketch uses ..." message to show up in the console pane.
- Momentarily connect the RST and GND pins on the Pro Micro.
Hopefully the sketch will now upload and your previously "bricked" Pro Micro will once again be recognized by the computer. After that, you can go back to uploading to the board normally without all this funny business of dummy ports and manual resets.
It might seem strange that I told you to unplug the working Pro Micro, since that causes its port to disappear. However, the Arduino IDE will still use the non-existent port for the auto reset process, which accomplishes nothing, but also doesn't result in an error, which is all we needed in this situation where you are going to manually reset the board.