About 20 years ago, he sent out invitations to his first fundraising breakfast. The very first reply envelope he got back had no return address and a crisp dollar bill in it.
He was very hurt and thought someone was trying to make fun of him. He was determined to find out who the sender was. He was obviously on the mailing list since he mailed the dollar in the reply envelope. Luckily he had a clue, the meter number, since it was metered postage, not a stamp. He called the post office but it was against their rules to say who the meter owner was. At this point he was absolutely driven, so he called the Post Office again and said he was in law enforcement and needed to know immediately. The guy believed him and told him who it was.
It was Merkos L'inyonei Chinuch...
The Rebbe? Perhaps. Hishtatfus.