The problem here is that if the Daisy chain is dropped and unpossessed, it is indistinguishable from a revealed A-T mine.
Well, of course you need to mark it with a "this is not an A-T minefield" counter.
Alternately you can mark your revealed A-T minefield counters with a "revealed A-T minefield" marker.
Either way your problem is solved. It's completely unreasonable to expect that players can just remember whether they placed an A-T minefield in a hex during setup, let alone assume that they are capable of looking up their scenario setup notes!
More seriously: I'd bet 20 cents that the B28 rules were written in the very early days of the rulebook composition, on the assumption that there would, indeed, be Daisy Chain counters in the countermix ... but saner heads prevailed, no such counters were created, and nobody thought to revise the text of the rule. (IMO quite a lot of Chapter B falls into the category of "nobody thought to revise the text of the rule".)