There's the legal stuff, which is fairly interesting, and then there's what actually happened, which can only be speculated at.
Looks to me like Deitrich had named his mother as beneficiary to his accounts in the case of his death first. Then he went to the bank to ask for that to be changed to name the Borg as beneficiary. Bank staffer tells him that he has to fill out new paperwork to make it happen. He probably is unsure of the exact name to put on it (Watch Tower Society, Watchtower Bible and Tract Society of Pennsylvania, Watchtower Bible and Tract Society of New York, Christian Congregation of Jehovah's Witnesses, Watch Tower, Faithful and Discreet Slave, Governing Body of Jehovah's Witnesses, or what?) or some other specific detail he doesn't have to hand, and so tells the bank staffer he'll find out exactly what to put on it and then come back. It slips his mind and he never comes back. In the meantime, the beneficiary has been changed to Watch Tower in the bank's computer as the staffer was typing it up during Deitrich's visit, but the hard copy paperwork never got completed.
Same sort of situation at the beginning but the bank was out of blank copies at the moment and the Xerox repairman was working on the copier at the time Deitrich was visiting the bank to change beneficiaries. Bank staffer apologizes for being unable to finish the changeover and can he please come back in an hour or so? Sure, he says, but he never does. Boom. Transaction is left completed in the computer but not on any hardcopy signed paperwork as required.
There are other scenarios that may have happened, too, but I think my speculations are the two most likely.