It truly is a sad thing for a country like Saudi Arabia to have non halal food. One would expect that if any country should sell only halal food, it would be Saudia Arabia, since they have the financial means and 'follow the Shariah'.
On the topic of questioning or having doubt whether something is halah or not, I was told this by a Shaykh.
Say there was two friends and a big mac. One believes that eating the big mac is not haraam, as he believes that eating non halal food is not haraam. The other friend believes that eating this big mac is indeed haraam because he trusts that eating non halal food makes one punishable. If both were to bite the burger, one would sin. The sinner being the one who believes that eating non halal food to be haraam. We know that intentions play a huge role in getting the reward for doing a good deed or becoming sinful. As in the hadith
"Allah's Apostle said, "The reward of deeds depends upon the intention and every person will get the reward according to what he has intended."Volume 1, Book 2, Number 51, Sahih Bukhari
One does not become sinful if he did not intend to disobey Allah. The sin of performing a Haram act is not registered as such except for someone who performs it with premedititation. As for someone who performs it out of ignorance, such a person is not blameworthy. However, even if the action is done out of ignorance, that does not necessarily cancel the worldly consequences. Nor does it save such a person from punishment if someone in his case should know better.
Overall, one must always ask the restaurant owner in which he is purchasing a meal from, the contents of that meal, whether it is a halal or not. Regardless it is in Saudi Arabia or Timbuktu. There are cheap people everywhere that will sell you anything, so you gotta be careful!
