No worries - these things happen =)

It can be pretty difficult to tell the differences based entirely on morphology. I think you would likely need to do a genitalia dissection to know for sure. Especially if the gene pool has been 'muddied' through time (i.e. F1 hybrids crossed to pure discoids and on down the line, subtle differences between the species will be even more difficult to tease apart). This is why the easiest and most certain way to determine would be to buy from a source with pure discoids... I know at one point a few years ago Kyle Kandilian from Roach Crossing (I call him the 'Roach King') was looking for 100% pure discoids and had a really hard time finding pure cultures.

For what it's worth, purity usually doesn't really matter unless you are a roach connoisseur/collector. Hybrids still make great feeders and can be just as, if not more fecund than pure species. But it can be a curveball for the FL residents who are working with the species for legal purposes.

When I get a chance I'll ask Kyle his thoughts. A while back I think he was doing genitalia dissections on the Eublaberus and Blaberus complexes (I think to differentiate the types like E. sp. "Ivory" and B. peruvianus from B. boliviensis and others Blaberus sp.).