For what it's worth, if I were told by a coral seller "I had bugs a month ago, and didn't treat, but don't see any now", it probably wouldn't change my decision if I wanted to buy a coral from you. But I would be warned and know that a preventative intercepter dip is in order, just to be on the safe side.
I don't think "most everyone nowadays" is dipping all their incoming corals in interceptor as a matter of everyday procedure (although we probably all should). My impression from talking to people is that it's less than half of SPS keepers that are using interceptor at all, and I think even among those there are far fewer who would treat with intercepter if they got a coral from a BRS member who assured them that they had "no pests" in their tank.
Personally I really think it's in everyone's best interest to be upfront about this sort of thing, because it is REALLY SIMPLE to treat one incoming coral that you suspect may have a chance of carrying the bugs. On the other hand, if one of your customers isn't warned, and doesn't treat, and by some odd chance manages to get the bugs in their entire stocked system it's a much bigger, more expensive and more risky treatment procedure to cure the whole system of them. Surely you can understand this, since you were so concerned about treating your system.
I just don't think you'll make this sale go any better for you if people worry that you're not being open with them. That's my take on it. I know you didn't ask, but hey, that's the problem with a bulletin board - we all think other people want to hear our opinions.
Good luck, Nate