Ref. No. 1018 Alif
In the name of Allah the Most Gracious the Most Merciful
The answer to your question is as follows:
If you tried to find out its owner and failed to reach him, then you should give that amount to any poor in Sadaqa, with the intention of sending the reward of this Sadaqa for the blessing and benefit of the owner.
And Allah knows best
Darul Uloom Waqf Deoband