story does not sound plausible
The story sounds strange. Why would a DC be accessible in the CS lab?
And if it really was it can't be an important system except for lab purposes.
If the lab is open for students on the weekend there would be a hotline to call in case of problems.
In the end if the student really "fixed" the DC I would have just left it at that and not tell anyone about it.
The situation before was "working", then it didn't, then it did again. No need to tell anybody why.