If you buy a 'hidden ticket' and fly from destination A to C with a stopover at point B (and you will leave the airport at destination B with a unused B to C leg), can you still accrue miles from the B to C leg? What if you checked in for the B to C leg but just didn't board the flight - can you get miles for this?
Frequent flyer miles are generally only earned when there's a "butt in seat", to quote the charming term of art from frequent flyer forums. If you don't show up at the gate and get your boarding pass scanned for the flight from B-C, you're going to be recorded as a no-show, and you're not going to get any miles for it either.
Also, while hidden-city ticketing is generally against the airline's T&C, it is almost certainly not "theft" in a criminal sense. But since the airline controls its frequent flyer scheme, you do run a real risk of losing your miles — even those flown "butt in seat" from A to B — if you do this too often.
There are exceptions caused by bad IT (for example, years ago BA code sharing onto Aer Lingus used to be famous for that) but in general the answer is no. It's also quite unpredictable because those kind of gaps don't really stay around for long.
Really air miles are not worth that much, the few extra you would collect from the B-C journey are not worth your time. If you really are into air miles you need a system to generate them en mass, either through flying every week on your employer's business (in which case the idea of doing flying on your day off quickly becomes unappetising) or something like manufactured spending.