@GloPro I am only giving my opinion here and as much as I would love to say time to celebrate your good fortune…I would hold off. IMO you should put in writing your demand to the bank that they disclose the source of these funds and ask that they put their reply in writing. At the very least ask for the name of the bank where this deposit came from and contact that bank to verify the veracity of the deposit. This way you have a written record of the banks position on this strange matter in case something more becomes of it.
I get wire transfers all the time and they always come with an ID of the source bank and bank account ID the money came from. Demand your bank provide this for you.
I have done a bit of searching on this type of event and in 99.9% of them there was a bank error. I left room for that one or two stories where it was a legit anonymous donor event I have yet to find.
Here are more links I found on mysterious deposits and their not so warm and fuzzy outcomes.
Bottom line you are on record that you contacted the bank over this deposit and that you are aware this was not your money. If and when anyone comes looking for it, you will be in possession of money that is not yours and you knew about it. How that plays out I cannot say. I truly hope this is an anonymous donor but like @longgone pointed out it is an odd sum that has me questioning what is really behind all this. Good luck!