What is the ruling on eating barbecue chicken pizza if the seller was not asked about its pork content, and this was remembered after receiving it?

The default ruling for the food of the People of the Book is permissibility. Doubt about the presence of pork in it does not render it forbidden, unless it is known that the predominant situation is the presence of pork. In such a case, one must inquire and refrain from consuming it if one doubts and does not inquire. If it becomes clear that there is any pork in the food, then it must be avoided. If a Muslim consumes food that, in reality, contained something forbidden, but this was not apparent to him, then he is not held accountable, and there is no sin upon him; because error is overlooked for the Ummah.