A student may hear one particular report from a senior authority only through an intermediary, and later directly hear another report from that authority. If the two occasions are confused and the first report is retold as direct, the original chain loses an intermediary.
This is not merely a synonym for the general topic of hidden disconnection: the distinctive pattern involves confusion between two actual occasions of hearing, producing an isnād interpolation.
Illustration: A student hears report A from teacher C through B, and later directly hears report B from C. If A is also presented as direct from C, comparative evidence can disclose the omitted B. The mere fact that two people met does not prove direct hearing of every report attributed between them.