I left a friend an expensive set of software. Later, I asked for it back. He responded that he had returned it to me.
He’s an honest friend, so I assumed I had misplaced the software. I needed a set, so I purchased a new set at great expense.
Some time later, he can back to me, and apologized, – he had erred. He had the software and returned it to me.
Is he obligated for the expense I occured purchasing a new set of software? In din? B’diney Shamayim?
Your friend does not appear to have any obligation of compensating you for the expense, even in dinei shamayim (which are reserved for particular types of damages, but not for every case in which an expense was incurred).
However, it would certainly be morally right for your friend to at least share in the expenses, though this falls short of any type of obligation.
Of course, you can try to minimize the damage by selling the software, or trying to return it to the store.
Good luck and best wishes.