Hi there Tess -
great to see you back, m'lady! And good to hear that you are recovering from the flu, it was really a long-lasting affair, if I recall correctly.
I agree with you: Slogsweep could have addressed the shop owner directly, thereby hopefully cutting off any further development of unnecessary fears. But I can very well understand why that did not happen. It is something that one has to learn, if one suffers from severe OCD. If I am right, I wrote something about this just prior to Christmas, about getting slowly used to crowded shops. Human contact is important, that's my experience. Ask where a desired item is; and in case of some accident, look for an assistant and tell what happened. IIRC, my personal and factual example was: I once dropped a bottle of wine, it burst, and the floor tiles got mega-red... the assistant told me not to worry at all and I didn't even have to pay for that bottle. It helped, really.
Your advice is excellent: boycotting won't help here, it would lead to anxiety and feelings of isolation, of being 'cut off' from the world outside, IMHO.
Hey, and I hope you'll quickly recover in full.
Best, Cuthbert.