I implemented a functionality necessary for anybody with more than one device.
In the forum footer box, along with the link to the rules, there is now two new links, one to 'Sync Read to Server' and the other is 'Get Read from Server'.
For now it's a clumsy work around to have the 'Thread is read' data available across devices like phone, tablet and computer. In the future it will be solved when I implement a proper data syncing method.
To use the new functionality is fairly simple. If you're accessing the forum on your computer and you need to leave the computer, click the 'Sync Read to Server', this will save the data to the site's server so that it's preserved and available for other devices.
If you need to access the forum on a different device, right before you start reading on the forum, click the 'Get Read from Server' link and it will download the read/unread data from the server (the same data that you saved). Then proceed to use the forum as usual, when you're done, click the 'Sync Read to Server' link.