I think as you are going through the install procedure, it asks you where to install it (or defaults to where it thinks it should go).
Looking in my Mac, it is in Applications folder.
PC (Windows 10) I found it in Program Files>Steinberg…
(not in Program Files (x86)) It also lists in the Start menu (bottom left), All apps menu, named Steinberg Dorico 2, and probably lists in the Notifications window at the right (as having been installed), then once opened, you can right-click on it on the taskbar and pin it there).
And if you’re searching, leave the “pro” out. There is only one Dorico 2 app, and it runs either as “pro” or as “elements” dependent on which licence is present.
If one is using a Mac, I have often found that upgrading leaves the original shortcut on the desktop and does not replace it or supplement it with the new shortcut icon even after the OS has installed the new version.