My interpretation from the manual is that if you disconnect from a machine (specifically, terminal) before trace is complete, then in 50 turns it returns to original state and can be hacked anew.
It would be nice if machines that are no longer hackable (because of completed trace) and those that are temporary in "better not connect" state are somehow indicated on a map. Cogmind is a robot, shouldn't have a problem tracking terminals he connected, how long ago and what was the outcome. I, on the other hand, would appreciate some help with this.
The situation when I wish for it, is when I am retracing my steps because dead end or just running for my life and back to terminal. I vaguely remember, I've been here. Maybe even remember the trace did not complete. But was it 50 turns ago? Have no idea, but I would really like another roll at Access(Main) or Alert(Purge).
On a similar note, some visual indication that fabricator is fabricating would be nice too. And maybe a query to tell ETA exactly if more precision is needed.