well - i think the issue with the flash drive and the phone seem more to be 2 different issues to me. i bought drives as well where some software was stored on - and it was little tools for backup-help or encrypting content on the device as was told already. i never use such and format new drives right away out of paranoia not using software that i dont know where it comes from.
having said that - of course you could construct a scenario where a hacked phone can have something to do with such. imagine, for example, your phone is connected to a pc for loading - it basically has the chance to communicate with that device - if not a 'load only' option was chosen - then the device does have access to the pc and/or the pc has access to the device - depending on how the security settings are, there is a potential to corrupt either device that way.
if anything is transfered from the device - may it be over usb, bluetooth or cloud - it is a potential risk - since what is transfered can be corrupted and thus can corrupt the receiving device as well. Same goes for anything transfered to the device - over the mentioned ways or from the app stores or any other sources.
a hacked account is usually a much worser scenario - since if an attacker gets access to a user's data in the cloud and is able to corrupt the data there - this can lead to an 'infection' of anything that has access to that data - since the nature of that is - to be used as a kind of central data-store. So a user connects with all his/her devices to that (because thats why users use the cloud) - thus it can lead to a corruption of all that devices as well. securing any account is thus one of the most important things all users should be aware of.
a relatively good article can be found here:
https://www.techlicious.com/tip/how-...s-been-hacked/