The mystery of the lost session

The Today’s puzzle is more challenging than the previous ones. I also admit that there might still be a solution other than the one we have found in the real case.
However, I just can not think of one.
But read for yourself:
One of our customers suffered from regular unpleasant row cache lock waits. The row cache lock was of type 7, which is dc_users. I created a system state dump, such as described here: system state dumps .
It was a whole series of blocked and blocking sessions in the dump.
If I wanted to find the blocking session in the dump to find out which statement was blocking, I could not find the session.
I also managed to find the SIDs of blocking sessions in real time. But the session itself was never there.
Which statement was issued by the blocking sessions?

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