Project Already Open
Happens to me every other day, since I forget to close Scrivener at work 
Using Dropbox for syncing.
Simple. Close Scrivener before leaving work. Ditto before leaving home. After, of course, allowing DropBox sufficient time to sync. Otherwise, you’ll encounter this… and also risk corruption in the event that something happens to your work or home computer while you aren’t there (power outage, administrator initiated reboot, …). Your work computer and Internet access is your employer’s computer, not yours. And Scrivener does not claim to support simultaneous access to a given project by two or more computers.
You should probably check to see what your employer’s policy is regarding use of non-employer supplied software and use of their computers and Internet for personal use.
It may be appropriate to bring your own device capable of accessing DropBox via public wifi or cellular, assuming that is permitted/supported. Desktop versions of Scrivener work on Apple laptops and on Windows laptops and Windows tablets. The iOS version of Scrivener works on iPhones and iPads. Some caution and routine practices are appropriate when using DropBox, as discussed in the following
scrivener.tenderapp.com/help/kb … c-services
and
scrivener.tenderapp.com/help/kb … g-with-ios
Or figure out a way (remote access, launchd or hazel-triggered AppleScript, Alfred remote, etc.) to remotely close Scrivener in your work machine.