Can you buy sliced watermelon from a supermarket?

can you buy sliced watermelon from a supermarket so a non-kosher knife can be assumed to have some kind of residue on it from the oil or fat that you cut in the past however the Ramones tells us that when you're talking about someone who cut a lot of fruit so first of all a fruit store can be assumed to have dedicated fruit knives and secondly even if it isn't dedicated after a cut a few fruit whatever leftover residue there was on the knife is already gone wiped away in bottle so therefore you can buy fruit sliced fruit from a fruit store or a supermarket where you know they've used that the knives and they've cut a ton of fruit however a restaurant or a caterer where they're going they cut the the fruit and then they cut the cake and they're going back and forth from kosher to non-kosher with just the wipe in between that would not be okay so buying from a restaurant or a caterer sliced to it or eating from a restaurant or cater a sliced fruit would not be okay for a fruit store or a supermarket that would be okay