is this wrong?

[branflake81]

Advert in magazine for Sainsburys: "And lots more instore"

Is "instore" even a word?

No. I'm pretty sure it isn't.

not yet but it will be soon

according to this, it is a word

but it doesn't mean what they meant when they used it

Oh Squonk, you're good.

it seems (to me) less offensive when used as an adjective modifying a noun - as in

lots more instore offers

is it just this jump to being used on its own as a prepositional phrase that grates i wonder