IDE 1.8.5 can't find Serial Port COM3 on Windows 8.1

Hello! I used my Arduino UNO for about an hour and suddenly
I couldn't upload. The problem was that COM3 just...
dissapeared from the Tools > Ports[/i} list. Not sure why though.
I've checked the device manager and if I go under Ports (COM & LPT),
I can see Arduino UNO (COM3) in the list. I'm really confused, because clearly
the Arduino is connected to the computer, and I've verified the code
and really all it is is this:
*void setup() {
  // put your setup code here, to run once:

void loop() {
  // put your main code here, to run repeatedly:
The only port I find in Tools > Ports is COM2, but before COM3 was there.
I'm really confused because it happened very suddenly, and I used, as I said before,
a long time with no problems at all. Help, please?