Say, logging into your account in a fashion which trips whatever heuristic they have for deciding if your account is compromised or just 'breaking their terms of service' with no further explanation. For example using 'suspicious' IPs like from some cloud provider, or from multiple countries in a short period of time, as these algorithms were written post-internet but pre-air travel. Who knows, honestly.

And yes this has happened to me, coincidentally after a period of travelling.

Some backed up hard drives in my house and a family member's are probably more reliable.

Sometimes nothing.