A while ago I put all my addresses with private keys (although they did not have that much money in them) onto a google keep note. I put it on a password protected notepad on my phone now, but could anyone have stolen them from my google keep note?
It'd be a huge violation of user trust if a Google employee looked at customer data and did something like that, so I'd say extremely unlikely.
That said, you shouldn't ever put your private keys on the internet.
Lastly, if this did happen and it involved any substantial amount of money, Google would be able to determine which employee accessed your data, which you could then very likely use in civil court to recover your stolen BTC.
Disclaimer: I work at Google.