It's not errata, but there's a chain of rules that can allow for this.
Casters can cancel any duration spell they cast within it's original casting radius. (it's in the spell notes)
Which, if I recall the original discussion relating to instances like this, means that casters are aware of all of their active spells that have durations, that they are standing within casting distance of.
So if the master entity spell has a casting range of 100', the caster will sense the control spell's existence as long as they are within 100' of the entity, if the spell fails or is cancelled 200' away, the caster won't know.
If the entity approaches, once it crosses that 100' line, the caster would be able to know.
That's in a grey area out at the edges of the rules, so it's not really clear if the caster just knows, or if they have to at least check "do I still feel the control spell" or if checking would require any effort like say concentration.