LW does say about Toby, despite his antics, his grades are good, and he usually knows how to toe the line and avoid serious trouble. LW simply never thought Toby would pull that prank on their co-worker (and hence LW), during what already sounded like a highly stressful time at work.

Did Toby know LW was expecting that call from work? Did LW explain to Toby how serious the call was? If yes, then certainly Toby was way out of line with his prank. He should have to apologize to the co-worker as part of his consequences.

But if Toby didn't know about the call--and imho it's not really clear from LW's letter that he did know--then I think maybe LW needs to cut him a bit of slack. At least, imho LW should not take out their embarrassment on Toby. Instead, as C&F says, LW should use this event as a teaching tool.

Either way, Toby absolutely needs to learn how to recognize when pranks are acceptable and when they aren't.