OK, first thank you.
Now, I unplugged the USB plug from its place and i plugged it into a different one.
I turned on the PC and i tested if it's OK now, and it did. (no disappearing)
Then, i unplugged the USB plug from the new place and i returned it back to the first plug and it is acting normal now.
What caused it? It wasn't good before the switching...
Sometimes the USB port doesn't work and need to be reset that way. I'm happy that your problem is fixed now