My understanding that advanced stone, shaped with metal, lasts. However, simple stone tools (think axes, hammers, flint arrowheads etc) tend to get easily lost. This is made furthermore difficult by the difficulty (impossibility?) of distinguishing them on tools like metal detectors
No, they're quite easy to find if you know what you're looking for and you look in the right places. Lithics in the ancient world were a bit like plastics today: ubiquitous and highly disposable.
For particular lithics industries/tools and certain situations you might get some amount of reworking, but ultimately people were producing new tools very frequently. That means that any area in which you might find them on the surface will usually have some and a long term production site will have overwhelming artifact density. They can occasionally look like normal rocks, but once you train your eye the worked faces become visually distinct.
