You saw the shared scooper being placed in a water basket between uses. It isn’t washed off. So residue ice cream from the non-kosher can remain on the scooper itself as well as there be non-kosher ice cream in the water basket the scooper is left in between uses.
These aren’t safeiks in the halachic kashrus sense. And you can’t trust the non-Jewish employees on kashrus matters in an uncertified food eatery that sells treif food. You’re simply eating non-kosher.