This happened to me[1] a decade ago, now. Left Apple hardware on shelf for a year or two, Apple in the mean time did their iCloud migration or something, and my login account could no longer unlock the device. It's been effectively bricked since.

[1] https://news.ycombinator.com/item?id=26482635

A similar thing happened to me - I lent a phone to my mother-in-law and created an account for her. She returned the phone once her own phone was fixed.

A few years passed, and a couple of weeks ago my phone broke, so I wanted to use that one until I bought a new one. It turned out that Apple had permanently deactivated the iCloud account on that phone. I could make calls, but I couldn’t install or update any apps, even though I still controlled the email address that was used to create the Apple account. Not that 5S is very useful these days but still.