Is the prayer acceptable if one prays in a place and then later discovers the presence of a cross around that same place?

The cross is a symbol of Christians that they venerate, believing that the Messiah was killed and crucified on it. This is a false belief that the Holy Quran refutes, as Allah Almighty says: (And they did not kill him, nor did they crucify him; but [another] was made to resemble him to them). The Prophet, peace and blessings be upon him, would not leave anything with crosses on it without removing it. Therefore, it is not permissible for Muslims to place the cross in their homes, on their furnishings, or in their mosques; rather, it must be removed. If a person prays on something with a cross or in a place where there is a cross, their prayer is valid, though disliked. They must avoid it in the future by removing the cross or replacing the item. However, if they did not know about the presence of the cross until after completing their prayer, there is no sin or dislike upon them, and their prayer is valid.