I found the following story online. As such this the “mekor”
The story occured Tuesday afternoon February 28 1978 or 21 Adar I 5738. He had justy finished giving a shiur on Atzutz Nakuv, when he asked for a coffee. ONe of the younger bachurim jumped at the oppurtunity and ran off to prepare it. Shortly after having the coffee the Rosh Yeshiva felt unwell and vomited. This was very unusual and created a big tumul. At first soem suspected the milk as it had been sitting out all day, but others drank the milk and were fine. This was really starnge. It was then that the mistake was realized. This young bachur and never prepared the Rosh Yeshiva’s coffee before and was understandibly nervous at the task at hand. He didnt double check the milk and accidently used a private bottle of instead don the Yeshiva’s cholov Yisroel milk.