Steam may be annoying and everything else but unless you have very specific desires and needs from that old build, there's no reason to not contact support to learn about your license transfer options. You should still be able to get your Steam key though. Not only some content will not work right, you won't be able to obtain it (or previous content for that matter) since sadly there no longer is a download page. But if you truly don't care about it yet and can't get a transfer, then you might as well wait for a sale while you keep playing your 1108 build.