Careful with tax implications!
Don't trust anyone.
Please go ahead and report it. I just don't think the interpretation will be so clear cut.
If OP really has no idea why the payment was sent and does not feel entitled to it, I'd judge it as not being income in the current year. While OP is in possession of it (per "cash basis"), it's only by clerical error. They're not free to do with the money as they'd like (eg spend it), and thus they're in the position of a trustee rather than someone who has received personal income. Remember, not every payment coming into your bank account is a taxable event.
If OP receives a 1099 for it, or they file their taxes and then receive a notice that the IRS has a 1099, then they declare it as income (since the 1099 indicates the payment had intent), distribute the money to themselves by moving it to a different account where it can't be ACH reversed, and consider the matter settled.
Failing that, if some time down the line Google confirms it as a legitimate payment or the clock runs out, then you distribute it to yourself and declare it as income at the time of distribution, regardless of the missing 1099.
Alternatively, if Google demands/pulls the payment back and you haven't paid taxes on it, case closed.
If Google does somehow issue a 1099 and then later ends up demanding the money back, then I'd say OP has a strong case that at the very least Google owes them for all the resulting damage of having to refile their taxes, etc. And given that OP is in possession of the money and outside the ACH reversal window, Google would have to mount a legal offense to get it back where OP could argue this point.
I mean technically if they fill a 1099 for this, the money is yours. Congratulations, you are now 250,000$ richer and owe back taxes to the IRS.
Sure you can refile your taxes then, but that will suck
Imagine you own land that has a parking lot on it. Someone parks their $250k lambo on your land and leaves it there for a few months. You don’t get taxed on that.
You certainly don’t report owning a new $250k lambo, and then later amend your tax return when the owner comes back, that would be a false report.
The conversation would probably go like this:
Dude: "Hey taxman Google sent me money but it's not mine"
IRS: "Ok don't spend it or it becomes income, if it turns out it was yours file an amended return. Contact us and reference this conversation and any penalties will be waived."
The IRS is not extremely accommodating and will not work with someone who is dishonest or evasive about their issues.
Yes, in most cases, government agencies will work with you and behave rationally. But one time in <some large number>, things go a different direction. And the people with the power can turn your life into a nightmare without batting an eyelash.
I would get a lawyer, someone that knows how to best protect you from the system.
Anyway the correct analogy here would be incorrectly receiving from someone you know payment in cash which should have been given to someone else. You realise the mistake when you are back home so you bring it back later. You obviously didn’t owe taxes while you were merely storing the money which wasn’t yours in the first place.