Hi,
This usually happens if the person moves and runs off to another part of the factory before they're all back. Before robot speed researches it can be especially prone to happening. Another possibility is you may have run past a (de)construction ghost at some point, and a robot deployed unnoticed - but it's essentially the same thing, moving out of range before they can return.
Since you were deconstructing trees, this scenario might be a little more likely: Perhaps some trees marked for deconstruction were just out of roboport range - it can be easy to miss the red X on them sometimes. So even if you stayed still as the robots worked and then waited until they all returned, when you started to leave they came into range for a moment. The construction bots deployed, but if you were looking towards your destination instead of at your character, it would have been very easy to not notice this.
Prevention
To prevent this from happening, I recommend remaining as still as possible or only moving short distances until all robots have returned. Further, turning off the roboports when not in use (default hotkey: alt R) can help avoid them deploying when not intended.
Recovery
The goods news - if this happens, the robots will eventually make their way back to you. Very slowly because they're out of power, but they will. If you've taken a train to another part of the base or otherwise moved a long distance it could be quite a while (this has happened to some friends of mine). But like the Terminator, they will not stop.
The one thing that could stop them is getting destroyed by biters, but you will receive a very noticeable alert if/when this happens.
Reset
Lastly, if you do not wish to wait for the robots to eventually find their way home to you, you can do the following to 'reset' the state of the mod, which will grant you a new mk0 armor and a set of robots:
1. Disable TinyStart.
2. Load your game.
3. Save your game.
4. Enable TinyStart.
5. Load your game.
Good luck out there and happy building!
