Hinges on what you believe would have happened to stock that scalpers bought, had they not done so. It may have left enough on the shelf for the would-be customers of scalpers to meet their needs. On the other hand, that leftover stock may have been obtained by panic buyers.
On a hunch I'd say a scalper would purchase more off the shelf than a panic buyer, because with the goal they have in mind they a) want a large quantity to resell to a large number of people and b) want to drain shelf stock to increase their odds of success.
that's why I used the toilet paper example. I don't think scalpers have enough storage space to clear an entire region's stockpile of tp. I did read a story of a guy who did exactly that with hand sanitizer, literally bought the entire supply from every store within 100 miles. that does change the analysis.
On a hunch I'd say a scalper would purchase more off the shelf than a panic buyer, because with the goal they have in mind they a) want a large quantity to resell to a large number of people and b) want to drain shelf stock to increase their odds of success.