For Sale: Brooks B17 £32 at Halfords

Viola, sorry to have offended with 'fuck'. 'Instore' is a bollocks word that seems to have only existed in the general sales speak since around the same time as 'online', also a hateful construct in my mind. I stand by my observation, albeit not worth a fig in your opinion.

I'd confidently say the existence of the term in(-)store pre-dates the web quite significantly as a term for a musical act or author doing an in(-)store appearance.
Admittedly its meaning is slightly different from the in(-)store you're complaining about. However as a word, it's existed for some time and quite reasonably describes a public appearance within a shop.