Might never have been a suit. At one point, J. Press sold jacket-vest combos intended to be worn with odd trousers (gray flannels, etc.). Weird, I know, but several people remember them when they were in the stores, and someone here or at AAAC found some deadstock ones not long ago. I think the ones I've seen or heard about were all tweed or other casual fabrics.
Interesting! This was a fairly standard, slightly rough 100% wool charcoal with pinstripe, which is why I thought it was probably an orphan.