Preventative officiating, or not?

[Dakota]

Unless there is something physical that makes one or the other of these players stand out, this is not something I would have noticed anyway.

ASA and NFHS handle this situation differently, and with different penalties. ASA allows the coach to "late announce" the re-entry, so long as it happens before the opposing coach protests. NFHS has no such allowance for the coach to "late announce", but OTOH, the NFHS penalty for the first occurance is much less severe than ASA's penalty.

Since NFHS does not allow for the late reporting of the re-entry, I think you should have also warned the coach/team about the unreported sub.