David Lang wrote:

Bag of loose mushrooms. placed on scale bit, touched fresh veg icon on
screen. Selected "L-M" icon which had a picture of a mushroom on it.
Screen opens, no mushrooms listed.

Probably under 'B' for button mushrooms, or if they're as idiosyncratic
as other supermarket self-checkouts (actually the newer Morrison tills
seem to have been upgraded to quad-hamster power, so they can keep up
with you).