How can I ask for forgiveness from the owner of a house from which I picked fruits when I was young, especially if he was a former tenant and has traveled, and what is the ruling if I am unable to find out his whereabouts or phone number?

If you took fruit that the tenant disliked you taking and did not give you permission, you must guarantee the value of what you took to its owner. If you are unable to reach the owner of the right, then give the value of what you took in charity on their behalf, as Ibn Taymiyyah mentioned for someone who despaired of knowing the owners of rights.