You can steal from a character that still has an account but is inactive though, if that's what you mean? i.e. ranked in a herd/outcast, has no absence up, but hasn't been played in months.
In order to steal/challenge for items back that were successfully stolen you need IC knowledge that a character has it on them by threading with them when it's in their records. Even though you can steal things originally from characters you've never met before, it doesn't work in reverse as a way to protect successful sneaks.
Helovia Hard Mode