Can you buy salad from a store or restaurant without a hashgacha?

can one buy a salad while traveling from a store without a hashak it's Rabbi belly's opinion that one is not allowed to based on three points one Mars Zion a person would see you going into a non- kosher restaurant they wouldn't see that you're only buying a salad and they would think that you're buying a regular meal number two the knives used to cut your salad could have just been used to cut non- kosher food number three is your salad has contains vegetables that require checking due to infestation