Not in my experience, no. Let's consider the plugged in item a lamp in this example.
The ones I have, smart plug that plugs into an existing socket and then the lamp plugs into that, include a physical on/off button on the smart plug, but if that is off, there's no power going to the lamp. Interacting with the lamp in that case is as if it isn't plugged in at all.
If the smart plug is on, you can certainly turn the lamp on and off the ol'fashioned way, but then it isn't using any smart capability. If the lamp is manually turned off via its own switch, even if the smart plug is on, the software control via the smart plug can't do anything with the lamp. The lamp has to have its switch on, and the smart plug must be on for any smart activity to work.
In the case of my smart plugs, as long as they are on, there is always power going to the lamp, thus it can be controlled manually if desired, no smart. But if the lamp is manually turned off, then turning it on via software even if the smart plug is still on won't work.
Hopefully I captured your use case there!
EDIT:
@sswilson got in ahead of me. If his answer is better, go with that
