He bought things and has not paid for them

Undoubtedly a person who buys something then does not pay for
it is stealing it, and stealing is a major sin, for which the Lawgiver has
stipulated the hadd punishment of cutting off the right hand: 

“And (as for) the male thief and the female thief, cut off
(from the wrist joint) their (right) hands as a recompense for that which
they committed, a punishment by way of example from Allaah”

[al-Maa’idah 5:38 – interpretation of the meaning]

The one who does this must also give back to people what is
rightfully theirs. Whoever does not this is exposing himself to punishment
and disgrace. 

It was narrated that Abu Humayd al-Saa’idi said: The
Messenger of Allaah (peace and blessings of Allaah be upon him) said:
“By Allaah, none of you takes something that is not rightfully his but he
will meet Allaah carrying it on the Day of Resurrection. I shall certainly
recognize some of you coming to meet Allaah carrying a camel bellowing, or a
cow mooing, or a sheep bleating.” Then he raised his hand so high that I
could see the whiteness of his armpit and said, “O Allaah, have I conveyed
(the message)?” (Narrated by al-Bukhaari, 6578; Muslim, 1832). 

This person can return the property to its owner in whatever
way he sees fit, without exposing his identity to him. If the person from
whom it was stolen is in a place that he cannot reach, or he does not know
who he is, then he has to give the value of the item in charity on behalf of
its owner. If he knows the person then he may give him the choice between
his accepting the fact that he gave charity on his behalf or taking what is
rightfully his. If he chooses the charity option, he will have the reward of
that, otherwise he (the thief) must give him what is rightfully his, and the
(reward for) charity will go to the one who has repented, if his repentance
is sincere. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

If you have stolen from a person or from an organization,
then you have to contact the person from whom you stole, and tell him “I
have such and such that belongs to you.” Then you have to come to an
agreement. But a person may feel that this is too difficult and that he
cannot go to a person and say – for example – “I stole such and such from
you and I took such and such from you.” In this case, he can make sure that
this money – for example – reaches him in another, indirect, manner. For
example, he could give it to one of the person’s friends, tell him the story
and say, “I have now repented to Allaah and I hope that you will give it to
him.” 

If he does that, then Allaah says (interpretation of the
meaning): 

“And whosoever fears Allaah and keeps his duty to Him, He
will make a way for him to get out (from every difficulty)”

[al-Talaaq 65:2] 

“and whosoever fears Allaah and keeps his duty to Him, He
will make his matter easy for him”

[al-Talaaq 65:4]

If we assume that you have stolen from someone and you do not
know who he is or where he is, then this is easier, because you can give in
charity an amount equal to what you stole, with the intention that the
reward be for the owner (of the stolen goods). In that case you will have
discharged your duty. 

The story told by the questioner shows that a person must
keep away from such things, because he may steal in a moment of ignorance
and foolishness, and not get caught, but then if Allaah blesses him with
guidance, he will have a hard time ridding himself of that. 

Fataawa Islamiyyah, 4/162 

The scholars of the Standing Committee said, concerning a
soldier who stole from a person: 

If he knows who the person is or knows someone who knows him,
then he has to look for him and give him his silver coins, or the
equivalent, or whatever he agrees upon with him. But if he does not know who
he is, or he thinks that he will never find him, then he should give an
equivalent amount of money in charity on behalf of the owner. Then if he
finds him after that, he should tell him what he has done. If he accepts
what he has done (giving charity), all well and good; and if does not accept
what he did and asks him for his money, he should give it to him, and the
(reward for) the charity will then be his. And he must ask Allaah for
forgiveness and repent to him, and make du’aa’ for the owner. 

Fataawa Islamiyyah, 4/165 

And Allaah knows best.