I stole some money and have since repented. I can’t return it as the company I stole from no longer exists. Does previous charity before I repented wipe away that debt?
You must do every thing you can to return the money to its owners either directly to them or to their inheritors if they are dead.
If you tried your best and could not reach to them, then it must be given to the Marja' of Taqleed who will distribute it to the poor as Majhool al-Maalik (unknown owner) on behalf of the real owners.
Wassalam.