Desdemona : Did she or didn't she?

I have this weird memory about high school Shakespeare class.  I can’t seem to find evidence for it in Google so I’m wondering if I throw it out here, if someone will perhaps know what I’m talking about. We were studying Othello.  We had our regular copy of the play, but also for some reason I recall that we had a photocopied version of some key scenes.  There is a quote from Othello about Desdemona where he says, “She loved me for the dangers I had passed, and I loved her that she did pity them.”  Fair enough.  But here’s the thing.  I remember that in one of the two versions we had, it clearly said “that she did not pity them” (emphasis mine).  I have vivid memories of pointing this out to the teacher and trying to make the argument that this said two very different things about Desdemona’s character.  We had gotten a brief taste of the whole “what did Shakespeare really write” argument with Hamlet’s “too, too solid/sullied flesh” speech, so I remember wondering if I had stumbled into another one.  I don’t recall where the debate went, although I think that she basically blew me off. And that’s where I’m stuck.  No amount of googling will tell me if there is a recognized edition of Othello that contains the line “that she did not pity them.”  So I’m left wondering if I imagined the whole thing.   Does anybody have any clue what I’m talking about?