The fact that you can't find it online or on their website might be that way for a reason. Of course you won't find a website that'll tell you "you better fess up about any past Greek affiliations or else we won't consider you for membership".

Given the nature of your situation and the fact that many NPHC members believe in DISCRETION, I really doubt you'll get much response here other than pointing you in a general direction. While GC is a WONDERFUL avenue for resources and advice, it's been my observation (both from interaction with NPHC members here on GreekChat and IRL) that sometimes it's not the most appropriate place to seek answers, especially about membership. Actually, it's not appropriate at all.

I'm not trying to be mean at all. That's just how it is.

I think you should just investigate the issue again on your own 2 years from now. You might feel comfortable more with one side of the issue than you do now.