It should list who in the message that has the document locked. This is different than checkout per SPO Admin's reply. But to my knowledge computer isn't logged. The only way to prevent the locking is to have supported office documents and a newer Office version that supports co-authoring.
If you turn on force of Checking out you can tell who has it and prevent locking, however it introduces a lot of other less than desirable usability for your users.
