I actually think you’re in a much better position now, because the MS was only subbed to one editor. That means if you do decide to query, you can mention that you were represented by Agent SoandSo, but the MS was only submitted to one editor before you parted ways amicably. I think most agents won’t be turned off by this, and also you’d get added points for the MS being strong enough to get repped.
This is the bright side I saw, too. But OH MAN does that suck. I am so sorry.