I got a chuckle out of reading your post as the first time I saw anyone use a plastic diffuser was an AP photographer back in the 80's. A lot of Photojournalists back then adopted the habit of making home made stofen like devices by cutting the bottom from a bottle of rubbing alcohol and sliding it over the face of the flash. It should be noted they didnt do that for any softening but more to get a decent spread of light while working in tight spaces with wide lenses. Most flashes back then did not have heads that automatically zoomed to match the lens width.
But was it a $50 cereal bowl?