Should we let them be since they have claimed that they were hacked, do we have the right to ask a mod to lock it and ask the OP to provide evidence and then they could unlock it themselves?
If a moderator locked your topic, you can unlock it.
If an admin locked your topic, you can not unlock it. I only don't know a global moderator has same power like forum admins in locking a topic.
If it is because of an account hack, the account can be frozen because of security issue, not only a topic. The user has to prove the actual ownership to get access to the account and access to his topics.