Per https://www.androidpolice.com/how-to-set-up-private-space-in-android-15/#hide-private-space-when-locked
When configuring private space to hide from the drawer when locked, there doesn't appear to be any mechanism to unlock it besides running through settings --> security --> private space.
According to above link, it should be possible to search in the drawer for "private space" in order to unlock it, but that doesn't seem to work in grapheneos launcher. Presumably its only in pixel launcher?