I see it here:
I've checked it here, and it works for me in Mx 7.4.0. I do see several apps and modules labeled as 'private' in the Desktop Modeler App store.
Some checks
1. Are you logged in as the same user in the Desktop Modeler as you used on the appstore.home.mendix.com site?
2. Does the module have still Draft status in the App store?