No - not a trick question., but maybe I didn't make myself clear.
Is there a way to discover such bad files other than trying to actually read from them one by one, say using cp or by sending a snapshot elsewhere?
As noted by your original email, ZFS reports on any corruption using the "zpool status" command.
ZFS detects corruption as part of its normal filesystem operations, which maybe triggered by: cp, send-recv, etc., or by a forced reading of the entire filesystem by scrub.
I am well aware that the file shown in zpool status -v is damaged and I have already restored it, but I wanted to know, if there're more of them.
Assuming that the ZFS filesystem in question is not degrading further (as in a disk going bad), upon completion of a successful scrub, zpool reports the complete status of the filesystem being reported on.