Yup, I've seen it happen more than once. The ones I saw didn't throw the covers away from the manhole leaving it completely uncovered, but they landed crookedly, partly over the hole.
I could see that happening if the cover was not quite completely seated in the rim of the manhole, but not if it’s all the way down flush with the street surface. Might the Con Edison work crew have left it just a little out of place?